JANUS ASPEN SERIES, 497, 1998-05-04

JANUS ASPEN SERIES
497, 1998-05-04

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JANUS ASPEN SERIES

Prospectus

MAY 1, 1998

This prospectus describes five mutual funds each of which has its own investment
objective, and policies (the "Portfolios"). Each Portfolio is a series of Janus
Aspen Series (the "Trust") and currently offers two classes of shares. The
Institutional Shares are sold under the name "Janus Aspen Series." The Trust is
registered with the Securities and Exchange Commission ("SEC") as an open-end
management investment company. The Institutional Shares of each Portfolio
(collectively, the "Shares") are offered by this prospectus in connection with
investment in and payments under variable annuity contracts and variable life
insurance contracts (collectively "variable insurance contracts"), as well as
certain qualified retirement plans. Janus Capital Corporation ("Janus Capital")
serves as investment adviser to each Portfolio. Janus Capital has been in the
investment advisory business for over 27 years and currently manages
approximately $80 billion in assets.

The Trust sells and redeems its Shares at net asset value without any sales
charges, commissions or redemption fees. Each variable insurance contract
involves fees and expenses not described in this Prospectus. Certain Portfolios
may not be available in connection with a particular contract and certain
contracts may limit allocations among the Portfolios. See the accompanying
contract prospectus for information regarding contract fees and expenses and any
restrictions on purchases or allocations.

This Prospectus contains information about the Shares that a prospective
purchaser of a variable insurance contract or plan participant should consider
before allocating purchase payments or premiums to the Portfolios. It should be
read carefully in conjunction with the separate account prospectus of the
specific insurance product that accompanies this Prospectus and retained for
future reference. Additional information about the Shares is contained in a
Statement of Additional Information ("SAI") filed with the SEC. The SAI dated
May 1, 1998 is incorporated by reference into this Prospectus. Copies of the SAI
are available upon request and without charge by writing or calling your
insurance company or plan sponsor.

FLEXIBLE INCOME PORTFOLIO MAY INVEST ALL OF ITS ASSETS IN HIGH-YIELD CORPORATE
DEBT SECURITIES, COMMONLY KNOWN AS "JUNK BONDS." SEE "ADDITIONAL RISK FACTORS"
ON PAGE 13 FOR THE RISKS ASSOCIATED WITH INVESTING IN THESE SECURITIES.

THESE SECURITIES HAVE NOT BEEN APPROVED BY THE SEC NOR HAS THE SEC PASSED ON THE
ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A
CRIMINAL OFFENSE.

THIS PROSPECTUS DOES NOT CONSTITUTE AN OFFER TO SELL SECURITIES IN ANY STATE OR
OTHER JURISDICTION TO ANY PERSON TO WHOM IT IS UNLAWFUL TO MAKE SUCH AN OFFER IN
SUCH STATE OR OTHER JURISDICTION.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

CONTENTS

<TABLE>
<S> <C>
PORTFOLIOS AT A GLANCE
Brief description of the Portfolios......................... 2
EXPENSE INFORMATION
Each Portfolio's annual operating expenses.................. 3
Financial Highlights - a summary of financial data.......... 4
PERFORMANCE TERMS
An explanation of performance terms......................... 7
THE PORTFOLIOS IN DETAIL
Investment Objectives and Policies.......................... 8
General Portfolio Policies.................................. 12
Additional Risk Factors..................................... 13
MANAGEMENT OF THE PORTFOLIOS
Investment Adviser and Investment Personnel................. 16
Personal Investing.......................................... 17
Management Expenses and Expense Limits...................... 17
Portfolio Transactions...................................... 17
Other Service Providers..................................... 17
Other Information........................................... 18
DISTRIBUTIONS AND TAXES
Distributions............................................... 19
Taxes....................................................... 19
SHAREHOLDER'S GUIDE
Purchases................................................... 20
Redemptions................................................. 20
Shareholder Communications.................................. 20
APPENDIX A
Glossary of Investment Terms................................ 21
APPENDIX B
Explanation of Rating Categories............................ 24
</TABLE>

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 1
<PAGE>

PORTFOLIOS AT A GLANCE

This section is designed to provide you with a brief overview of the Portfolios
and their investment emphasis. A more detailed discussion of the Portfolios'
investment objectives and policies begins on page 8.

GROWTH PORTFOLIO
Focus: A diversified portfolio that seeks long-term growth of capital by
investing primarily in common stocks, with an emphasis on companies with larger
market capitalizations.
Inception: September 1993
Manager: James P. Craig, III
Assistant Managers:David C. Decker
Blaine P. Rollins

AGGRESSIVE GROWTH PORTFOLIO
Focus: A nondiversified portfolio that seeks long-term growth of capital by
investing primarily in common stocks, with an emphasis on securities issued by
medium-sized companies.
Inception: September 1993
Manager: James P. Goff

WORLDWIDE GROWTH PORTFOLIO
Focus: A diversified portfolio that seeks long-term growth of capital by
investing primarily in common stocks of foreign and domestic issuers.
Inception: September 1993
Manager: Helen Young Hayes
Assistant Manager: Laurence J. Chang

BALANCED PORTFOLIO
Focus: A diversified portfolio that seeks long-term growth of capital, balanced
by current income. The Portfolio normally invests 40-60% of its assets in
securities selected primarily for their growth potential and 40-60% of its
assets in securities selected primarily for their income potential.
Inception: September 1993
Manager: Blaine P. Rollins

FLEXIBLE INCOME PORTFOLIO
Focus: A diversified portfolio that seeks to maximize total return from a
combination of income and capital appreciation by investing primarily in
income-producing securities.
Inception: September 1993
Manager: Ronald V. Speaker

2 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

EXPENSE INFORMATION

The following tables and example are designed to assist participants in
qualified plans that invest in the Shares of the Portfolios in understanding the
various costs and expenses that you will bear directly or indirectly as an
investor in the Shares. OWNERS OF VARIABLE INSURANCE CONTRACTS THAT INVEST IN
THE SHARES SHOULD REFER TO THE VARIABLE INSURANCE CONTRACT PROSPECTUS FOR A
DESCRIPTION OF COSTS AND EXPENSES, AS THE TABLES AND EXAMPLE DO NOT REFLECT
DEDUCTIONS AT THE SEPARATE ACCOUNT LEVEL OR CONTRACT LEVEL FOR ANY CHARGES THAT
MAY BE INCURRED UNDER A CONTRACT.

SHAREHOLDER TRANSACTION EXPENSES (applicable to each Portfolio)

<TABLE>
<S> <C>
Maximum sales load imposed on purchases None
Maximum sales load imposed on reinvested dividends None
Deferred sales charges on redemptions None
Redemption fee None
Exchange fee None
</TABLE>

ANNUAL OPERATING EXPENSES (after fee waivers and reductions)(1)
(expressed as a percentage of average net assets)

<TABLE>
<CAPTION>
- -----------------------------------------------------------------------------------------------------------------
MANAGEMENT OTHER TOTAL OPERATING
FEE EXPENSES EXPENSES
- -----------------------------------------------------------------------------------------------------------------
<S> <C> <C> <C>
Growth Portfolio 0.65% 0.05% 0.70%
Aggressive Growth Portfolio 0.73% 0.03% 0.76%
Worldwide Growth Portfolio 0.66% 0.08% 0.74%
Balanced Portfolio 0.76% 0.07% 0.83%
Flexible Income Portfolio 0.65% 0.10% 0.75%
----------------------------------------------------------------------------------------------------------------
</TABLE>

(1) Management fees for Growth, Aggressive Growth, Worldwide Growth and Balanced
Portfolios reflect a reduced fee schedule effective July 1, 1997. The
management fee for each of these Portfolios reflects the new rate applied to
net assets as of December 31, 1997. Other expenses are based on gross
expenses of the Shares before expense offset arrangements for the fiscal
year ended December 31, 1997. The information for each Portfolio other than
the Flexible Income Portfolio is net of fee reductions from Janus Capital.
Fee reductions for Growth, Aggressive Growth, Worldwide Growth and Balanced
Portfolios reduce the management fee to the level of the corresponding Janus
retail fund. Without such reductions, the Management Fee, Other Expenses and
Total Operating Expenses would have been 0.74%, 0.04% and 0.78% for Growth
Portfolio; 0.74%, 0.04% and 0.78% for Aggressive Growth Portfolio; 0.72%,
0.09% and 0.81% for Worldwide Growth Portfolio; and 0.77%, 0.06% and 0.83%
for Balanced Portfolio, respectively. Janus Capital may modify or terminate
the reductions at any time upon at least 90 days' notice to the Trustees.

EXAMPLE

Assume you invest $1,000, the Shares of the Portfolios return 5% annually and
each Portfolio's expense ratio remains as listed above. The example below shows
the operating expenses that you would indirectly bear as an investor in the
Shares of the Portfolios.

<TABLE>
<CAPTION>
- ---------------------------------------------------------------------------------------------------------------
1 YEAR 3 YEARS 5 YEARS 10 YEARS
- ---------------------------------------------------------------------------------------------------------------
<S> <C> <C> <C> <C>
Growth Portfolio $7 $22 $39 $ 87
Aggressive Growth Portfolio $8 $24 $42 $ 94
Worldwide Growth Portfolio $8 $24 $41 $ 92
Balanced Portfolio $8 $26 $46 $103
Flexible Income Portfolio $8 $24 $42 $ 93
--------------------------------------------------------------------------------------------------------------
</TABLE>

THE EXAMPLE SHOULD NOT BE CONSIDERED A REPRESENTATION OF PAST OR FUTURE RETURNS
OR EXPENSES WHICH MAY BE MORE OR LESS THAN THOSE SHOWN.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 3
<PAGE>

FINANCIAL HIGHLIGHTS

Unless otherwise noted, the information below is for fiscal periods ending on
December 31st of each year. The accounting firm of Price Waterhouse LLP has
audited the Portfolios' financial statements since their inception. Their report
is included in the Portfolios' Annual Report, which is incorporated by reference
into the SAI. A DETAILED EXPLANATION OF THE FINANCIAL HIGHLIGHTS CAN BE FOUND ON
PAGE 6.
<TABLE>
<CAPTION>
GROWTH PORTFOLIO
INSTITUTIONAL SHARES 1997 1996 1995 1994 1993(1)
- -----------------------------------------------------------------------------------------------------------
<C> <S> <C> <C> <C> <C> <C>
1. Net asset value, beginning of period $15.51 $13.45 $10.57 $10.32 $10.00
- -----------------------------------------------------------------------------------------------------------
INCOME FROM INVESTMENT OPERATIONS:
2. Net investment income .15 .17 .28 .09 .03
3. Net gains or (losses) on securities
(both realized and unrealized) 3.34 2.29 2.90 .20 .32
- -----------------------------------------------------------------------------------------------------------
4. Total from investment operations 3.49 2.46 3.18 .29 .35
- -----------------------------------------------------------------------------------------------------------
LESS DISTRIBUTIONS:
5. Dividends (from net investment income) (.15) (.17) (.30) (.04) (.03)
6. Tax return of capital distributions -- -- -- -- --
7. Distributions (from capital gains) (.37) (.23) -- -- --
- -----------------------------------------------------------------------------------------------------------
8. Total distributions (.52) (.40) (.30) (.04) (.03)
- -----------------------------------------------------------------------------------------------------------
9. Net asset value, end of period $18.48 $15.51 $13.45 $10.57 $10.32
- -----------------------------------------------------------------------------------------------------------
10. Total return* 22.75% 18.45% 30.17% 2.76% 3.50%
- -----------------------------------------------------------------------------------------------------------
11. Net assets, end of period (in
thousands) $608,281 $325,789 $126,911 $43,549 $7,482
12. Average net assets for the period (in
thousands) $477,914 $216,125 $77,344 $26,464 $3,191
13. Ratio of gross expenses to average net
assets** 0.70%(7) 0.69%(6) 0.78%(5) N/A N/A
14. Ratio of net expenses to average net
assets** 0.69% 0.69% 0.76% 0.88%(2)(4) 0.25%(3)
15. Ratio of net investment income to
average net assets** 0.91% 1.39% 1.24% 1.45% 2.54%
16. Portfolio turnover rate** 122% 87% 185% 169% 162%
17. Average commission rate $0.0500 $0.0466 N/A N/A N/A
- -----------------------------------------------------------------------------------------------------------

<CAPTION>
AGGRESSIVE GROWTH PORTFOLIO
1997 1996 1995 1994 1993(1)

<C> <C> <C> <C> <C> <C>
1. $18.24 $17.08 $13.62 $11.80 $10.00
- -------------------------------------------------------------------

2. -- -- .24 .11 .01
3.
2.31 1.36 3.47 1.82 1.80
- -------------------------------------------------------------------
4. 2.31 1.36 3.71 1.93 1.81
- -------------------------------------------------------------------

5. -- -- (.25) (.11) (.01)
6. -- (.01) -- -- --
7. -- (.19) -- -- --
- -------------------------------------------------------------------
8. -- (.20) (.25) (.11) (.01)
- -------------------------------------------------------------------
9. $20.55 $18.24 $17.08 $13.62 $11.80
- -------------------------------------------------------------------
10. 12.66% 7.95% 27.48% 16.33% 18.05%
- -------------------------------------------------------------------
11.
$508,198 $383,693 $185,911 $41,289 $1,985
12.
$418,464 $290,629 $107,582 $14,152 $1,091
13.
0.76%(7) 0.76%(6) 0.86%(5) N/A N/A
14.
0.76% 0.76% 0.84% 1.05%(2)(4) 0.25%(3)
15.
(0.10%) (0.27%) 0.58% 2.18% 0.34%
16. 130% 88% 155% 259% 31%
17. $0.0367 $0.0347 N/A N/A N/A
- -------------------------------------------------------------------
</TABLE>
<TABLE>
<CAPTION>
WORLDWIDE GROWTH PORTFOLIO
INSTITUTIONAL SHARES 1997 1996 1995 1994 1993(1)
- -------------------------------------------------------------------------------------------------------------
<C> <S> <C> <C> <C> <C> <C>
1. Net asset value, beginning of period $19.44 $15.31 $12.07 $11.89 $10.00
- -------------------------------------------------------------------------------------------------------------
INCOME FROM INVESTMENT OPERATIONS:
2. Net investment income .16 .16 .11 .04 .02
3. Net gains or (losses) on securities
(both realized and unrealized) 4.14 4.27 3.19 .14 1.89
- -------------------------------------------------------------------------------------------------------------
4. Total from investment operations 4.30 4.43 3.30 .18 1.91
- -------------------------------------------------------------------------------------------------------------
LESS DISTRIBUTIONS:
5. Dividends (from net investment income) (.17) (.17) (.06) -- (.01)
6. Dividends (in excess of net investment
income) (.02) -- -- -- --
7. Tax return of capital distributions -- -- -- -- --
8. Distributions (from capital gains) (.16) (.13) -- -- (.01)
- -------------------------------------------------------------------------------------------------------------
9. Total distributions (.35) (.30) (.06) -- (.02)
- -------------------------------------------------------------------------------------------------------------
10. Net asset value, end of period $23.39 $19.44 $15.31 $12.07 $11.89
- -------------------------------------------------------------------------------------------------------------
11. Total return* 22.15% 29.04% 27.37% 1.53% 19.10%
- -------------------------------------------------------------------------------------------------------------
12. Net assets, end of period (in thousands) $1,576,548 $582,603 $108,563 $37,728 $4,856
13. Average net assets for the period (in
thousands) $1,148,951 $304,111 $59,440 $22,896 $2,200
14. Ratio of gross expenses to average net
assets** 0.74%(7) 0.80%(6) 0.90%(5) N/A N/A
15. Ratio of net expenses to average net
assets** 0.74% 0.80% 0.87% 1.18%(2)(4) 0.25%(3)
16. Ratio of net investment income to
average net assets** 0.67% 0.83% 0.95% 0.50% 0.84%
17. Portfolio turnover rate** 80% 62% 113% 217% 57%
18. Average commission rate $0.0337 $0.0345 N/A N/A N/A
- -------------------------------------------------------------------------------------------------------------

<CAPTION>
BALANCED PORTFOLIO
1997 1996 1995 1994 1993(1)
- ----------------------------------------------------------------------------------------------------------
<C> <C> <C> <C> <C> <C>
1. $14.77 $13.03 $10.63 $10.64 $10.00
- -------------------------------------------------------------------------------------------------------------

2. .34 .32 .17 .15 .08
3.
2.89 1.81 2.45 (.06) .64
- -------------------------------------------------------------------------------------------------------------
4. 3.23 2.13 2.62 .09 .72
- -------------------------------------------------------------------------------------------------------------

5. (.35) (.30) (.22) (.10) (.08)
6.
-- -- -- -- --
7. -- -- -- -- --
8. (.18) (.09) -- -- --
- -------------------------------------------------------------------------------------------------------------
9. (.53) (.39) (.22) (.10) (.08)
- -------------------------------------------------------------------------------------------------------------
10. $17.47 $14.77 $13.03 $10.63 $10.64
- -------------------------------------------------------------------------------------------------------------
11. 22.10% 16.18% 24.79% 0.84% 7.20%
- -------------------------------------------------------------------------------------------------------------
12. $362,409 $85,480 $14,021 $3,153 $537
13.
$176,432 $43,414 $5,739 $2,336 $521
14.
0.83%(7) 0.94%(6) 1.37%(5) N/A N/A
15.
0.82% 0.92% 1.30% 1.57%(2)(4) 0.25%(3)
16.
2.87% 2.92% 2.41% 1.90% 2.69%
17. 139% 103% 149% 158% 126%
18. $0.0456 $0.0426 N/A N/A N/A
- -------------------------------------------------------------------------------------------------------------
</TABLE>

* Total return not annualized for periods of less than one year.
** Annualized for periods of less than one full year.
(1) September 13, 1993 (inception) to December 31, 1993.
(2) Commissions payable by the Portfolio for transactions effected by a
broker-dealer affiliated with Janus Capital were credited against the
Portfolio's operating expenses. The effect of such directed brokerage
arrangement was de minimis.
(3) The ratio was 2.16%, 5.79%, 2.71% and 7.92%, respectively, for Growth,
Aggressive Growth, Worldwide Growth and Balanced Portfolios, before waiver
of certain fees and/or voluntary reduction of adviser's fees to the
effective rate of the corresponding Janus retail fund.
(4) The ratio was 1.23%, 1.14%, 1.49% and 1.74%, respectively, for Growth,
Aggressive Growth, Worldwide Growth and Balanced Portfolios, before
voluntary reduction of adviser's fees to the effective rate of the
corresponding Janus retail fund.
(5) The ratio was 0.98%, 0.93%, 1.09% and 1.55%, respectively, for Growth,
Aggressive Growth, Worldwide Growth and Balanced Portfolios, before
voluntary reduction of adviser's fees to the effective rate of the
corresponding Janus retail fund.
(6) The ratio was 0.83%, 0.83%, 0.91% and 1.07%, respectively, for Growth,
Aggressive Growth, Worldwide Growth and Balanced Portfolios, before
voluntary reduction of adviser's fees to the effective rate of the
corresponding Janus retail fund.
(7) The ratio was 0.78%, 0.78%, 0.81% and 0.83% respectively for Growth,
Aggressive Growth, Worldwide Growth and Balanced Portfolios, before
voluntary reduction of adviser's fees to the effective rate of the
corresponding Janus retail fund.

4 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

<TABLE>
<CAPTION>
FLEXIBLE INCOME PORTFOLIO
INSTITUTIONAL SHARES 1997 1996 1995 1994 1993(1)
- -------------------------------------------------------------------------------------------------------------------------
<C> <S> <C> <C> <C> <C> <C>
1. Net asset value, beginning of period $11.24 $11.11 $9.48 $9.97 $10.00
- -------------------------------------------------------------------------------------------------------------------------
INCOME FROM INVESTMENT OPERATIONS:
2. Net investment income .67 .74 .53 .47 .11
3. Net gains or (losses) on securities (both realized and
unrealized) .62 .24 1.70 (.56) (.04)
- -------------------------------------------------------------------------------------------------------------------------
4. Total from investment operations 1.29 .98 2.23 (.09) .07
- -------------------------------------------------------------------------------------------------------------------------
LESS DISTRIBUTIONS:
5. Dividends (from net investment income) (.64) (.72) (.60) (.40) (.10)
6. Tax return of capital distributions -- -- -- -- --
7. Distributions (from capital gains) (.11) (.13) -- -- --
- -------------------------------------------------------------------------------------------------------------------------
8. Total distributions (.75) (.85) (.60) (.40) (.10)
- -------------------------------------------------------------------------------------------------------------------------
9. Net asset value, end of period $11.78 $11.24 $11.11 $9.48 $9.97
- -------------------------------------------------------------------------------------------------------------------------
10. Total return* 11.76% 9.19% 23.86% (0.91%) 0.70%
- -------------------------------------------------------------------------------------------------------------------------
11. Net assets, end of period (in thousands) $54,098 $25,315 $10,831 $1,924 $538
12. Average net assets for the period (in thousands) $36,547 $17,889 $5,556 $1,636 $497
13. Ratio of gross expenses to average net assets** 0.75% 0.84% 1.07% N/A N/A
14. Ratio of net expenses to average net assets** 0.75% 0.83% 1.00% 1.00%(3) 1.00%(2)
15. Ratio of net investment income to average net assets** 6.90% 7.31% 7.46% 5.49% 3.77%
16. Portfolio turnover rate** 119% 250% 236% 234% 508%
- -------------------------------------------------------------------------------------------------------------------------
</TABLE>

* Total return not annualized for periods of less than one year.
** Annualized for periods of less than one full year.
(1) September 13, 1993 (inception) to December 31, 1993.
(2) The ratio was 5.27% for the Flexible Income Portfolio, before waiver of
certain fees incurred by the Portfolio.
(3) The ratio was 1.35% for the Flexible Income Portfolio, before waiver of
certain fees incurred by the Portfolio.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 5
<PAGE>

UNDERSTANDING THE
FINANCIAL HIGHLIGHTS

This section is designed to help you better understand the information
summarized in the Financial Highlights tables. The tables contain important
historical operating information that may be useful in making your investment
decision or understanding how your investment has performed. The Portfolios'
Annual Report contains additional information about each Portfolio's
performance, including a comparison to an appropriate securities index. To
request a copy of the Annual Report, please call or write your insurance
company.

NET ASSET VALUE ("NAV") is the value of a single Share of a Portfolio. It is
computed by adding the value of all of a Portfolio's investments and other
assets, subtracting any liabilities and dividing the result by the number of
shares outstanding. The difference between NET ASSET VALUE, BEGINNING OF PERIOD,
and NET ASSET VALUE, END OF PERIOD in the Financial Highlights tables represents
the change in value of a Share of a Portfolio over the fiscal period, but not
its total return.

NET INVESTMENT INCOME is the per share amount of dividends and interest income
earned on securities held by a Portfolio, less Portfolio expenses. DIVIDENDS
(FROM NET INVESTMENT INCOME) are the per share amount that a Portfolio paid from
net investment income.

NET GAINS OR (LOSSES) ON SECURITIES is the per share increase or decrease in
value of the securities a Portfolio holds. A gain (or loss) is realized when
securities are sold. A gain (or loss) is unrealized when securities increase or
decrease in value but are not sold. DISTRIBUTIONS (FROM CAPITAL GAINS) are the
per share amount that a Portfolio paid from net realized gains.

TOTAL RETURN is the percentage increase or decrease in the value of an
investment over a stated period of time. Total return includes both changes in
NAV and income. For the purposes of calculating total return, it is assumed that
dividends and distributions are reinvested at the NAV on the day of the
distribution.

RATIO OF GROSS EXPENSES TO AVERAGE NET ASSETS is the total of a Portfolio's
operating expenses before expense offset arrangements divided by its average net
assets for the stated period. The Portfolios were not required to disclose the
ratio of gross expenses to average net assets prior to 1995. RATIO OF NET
EXPENSES TO AVERAGE NET ASSETS reflects reductions in a Portfolio's expenses
through the use of brokerage commissions and uninvested cash balances earning
interest or balance credits.

RATIO OF NET INVESTMENT INCOME TO AVERAGE NET ASSETS is a Portfolio's net
investment income divided by its average net assets for the stated period.

PORTFOLIO TURNOVER RATE is a measure of the amount of a Portfolio's buying and
selling activity. It is computed by dividing total purchases or sales, whichever
is less, by the average monthly market value of a Portfolio's securities.

AVERAGE COMMISSION RATE is the total of a Portfolio's agency commission paid on
equity securities trades divided by the number of shares purchased and sold.

6 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

PERFORMANCE TERMS

This section will help you understand various terms that are commonly used to
describe a Portfolio's performance. You may see references to these terms in our
newsletters or advertisements (or those published by participating insurance
companies) and in media articles. Newsletters and advertisements may include
comparisons of a Portfolio's performance to the performance of other mutual
funds, mutual fund averages or recognized stock market indices. Growth
Portfolio, Aggressive Growth Portfolio, Worldwide Growth Portfolio and Balanced
Portfolio generally measure performance in terms of total return, while Flexible
Income Portfolio generally uses yield.

CUMULATIVE TOTAL RETURN represents the actual rate of return on an investment
for a specified period. The Financial Highlights tables show total return for a
single fiscal period. Cumulative total return is generally quoted for more than
one year (e.g., the life of a Portfolio). A cumulative total return does not
show interim fluctuations in the value of an investment.

AVERAGE ANNUAL TOTAL RETURN represents the average annual percentage change of
an investment over a specified period. It is calculated by taking the cumulative
total return for the stated period and determining what constant annual return
would have produced the same cumulative return. Average annual returns for more
than one year tend to smooth out variations in a Portfolio's return and are not
the same as actual annual results.

YIELD shows the rate of income the Shares earn on investments as a percentage of
the Portfolio's share price. It is calculated by dividing a Portfolio's net
investment income for a 30-day period by the average number of Shares entitled
to receive dividends and dividing the result by the Share's NAV per share at the
end of the 30-day period. Yield does not include changes in NAV.

Yields are calculated according to standardized SEC formulas and may not equal
the income on an investor's account. Yield is usually quoted on an annualized
basis. An annualized yield represents the amount you would earn if you remained
in a Portfolio for a year and the Shares of that Portfolio continued to have the
same yield for the entire year.

THE PORTFOLIOS IMPOSE NO SALES OR OTHER CHARGES THAT WOULD AFFECT TOTAL RETURN
OR YIELD COMPUTATIONS. YIELD AND TOTAL RETURN FIGURES OF THE PORTFOLIOS INCLUDE
THE EFFECT OF DEDUCTING EACH PORTFOLIO'S EXPENSES, BUT MAY NOT INCLUDE CHARGES
AND EXPENSES ATTRIBUTABLE TO ANY PARTICULAR INSURANCE PRODUCT. PORTFOLIO
PERFORMANCE FIGURES ARE BASED UPON HISTORICAL RESULTS AND ARE NOT INTENDED TO
INDICATE FUTURE PERFORMANCE. INVESTMENT RETURNS AND NET ASSET VALUE WILL
FLUCTUATE SO THAT SHARES, WHEN REDEEMED, MAY BE WORTH MORE OR LESS THAN THEIR
ORIGINAL COST.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 7
<PAGE>

THE PORTFOLIOS IN DETAIL

This section takes a closer look at the Portfolios' investment objectives,
policies and the securities in which they invest. Please carefully review the
"Additional Risk Factors" section of this Prospectus for a more detailed
discussion of the risks associated with certain investment techniques. Appendix
A contains a more detailed description of investment terms used throughout this
Prospectus. You should carefully consider your investment goals, time horizon
and risk tolerance before choosing a Portfolio.

Each Portfolio has an investment objective and policies that are similar to
those of a Janus retail fund, as illustrated in the chart on this page. Although
it is anticipated that each Portfolio and its corresponding retail fund will
hold similar securities, differences in asset size and cash flow needs as well
as the relative weightings of securities selections may result in differences in
investment performance. Expenses of each Portfolio and its corresponding retail
fund are expected to differ. The variable contract owner will also bear various
insurance-related costs at the insurance company level. You should review the
accompanying separate account prospectus for a summary of contract fees and
expenses.

Policies that are noted as "fundamental" cannot be changed without a shareholder
vote. All other policies, including each Portfolio's investment objective, are
not fundamental and may be changed by the Portfolios' Trustees without a
shareholder vote. You will be notified of any such changes that are material. If
there is a material change in a Portfolio's objective or policies, you should
consider whether that Portfolio remains an appropriate investment for your
variable insurance contract or qualified retirement plan.
EACH OF THE PORTFOLIOS HAS A SIMILAR INVESTMENT
OBJECTIVE AND SIMILAR INVESTMENT POLICIES TO AN EXISTING JANUS RETAIL FUND.

Growth Portfolio....................................................Janus Fund
Aggressive Growth Portfolio..............................Janus Enterprise Fund
Worldwide Growth Portfolio................................Janus Worldwide Fund
Balanced Portfolio.........................................Janus Balanced Fund
Flexible Income Portfolio...........................Janus Flexible Income Fund

GROWTH PORTFOLIO, AGGRESSIVE GROWTH PORTFOLIO AND WORLDWIDE GROWTH PORTFOLIO ARE
DESIGNED FOR LONG-TERM INVESTORS WHO SEEK GROWTH OF CAPITAL ONLY AND WHO CAN
TOLERATE THE GREATER RISKS ASSOCIATED WITH COMMON STOCK INVESTMENTS.

GROWTH PORTFOLIOS
Investment Objective:..........................................Growth of Capital
Primary Holdings:..................................................Common Stocks
Shareholder's Investment Horizon:......................................Long-Term

GROWTH PORTFOLIO
The investment objective of this Portfolio is long-term growth of capital in a
manner consistent with the preservation of capital. It is a diversified
portfolio that pursues its objective by investing primarily in common stocks of
issuers of any size. This Portfolio generally invests in larger, more
established issuers.

AGGRESSIVE GROWTH PORTFOLIO
The investment objective of this Portfolio is long-term growth of capital. It is
a nondiversified portfolio that pursues its investment objective by normally
investing at least 50% of its equity assets in securities issued by medium-sized
companies. Medium-sized companies are those whose market capitalizations fall
within the range of companies in the S&P MidCap 400 Index (the "MidCap Index").
Companies whose capitalization falls outside this range after the Portfolio's
initial purchase continue to be considered medium-sized companies for the
purpose of this policy. As of December 31, 1997, the MidCap Index included
companies with capitalizations between approximately $213 million and $13.7
billion. The range of the MidCap Index is expected to change on a regular basis.
Subject to the above policy, the Portfolio may also invest in smaller or larger
issuers.

WORLDWIDE GROWTH PORTFOLIO
The investment objective of this Portfolio is long-term growth of capital in a
manner consistent with the preservation of capital. It is a diversified
portfolio that pursues its objective primarily through investments in common
stocks of foreign and domestic issuers. The Portfolio has the flexibility to
invest on a worldwide basis in companies and other organizations of any size,
regardless of country of organization or place of principal business activity.
Worldwide Growth Portfolio normally invests in issuers from at least five
different countries, including the United States. The Portfolio may at times
invest in fewer than five countries or even a single country.

TYPES OF INVESTMENTS
Each of these Portfolios invests primarily in common stocks of foreign and
domestic companies. However, the percentage of each Portfolio's assets invested
in common stocks will vary and each Portfolio may at times hold substantial
positions in cash equivalents or interest bearing securities. See "General
Portfolio Policies" on page 12. Each Portfolio may invest to a lesser degree in
other types of securities including preferred stocks, warrants, convertible
securities and debt securities when its portfolio manager perceives an
opportunity for capital growth from such securities or to receive a return on
idle cash. Some securities that the Portfolios purchase may be on a when-issued,
delayed delivery or forward commitment basis. The Portfolios may invest up to
25% of their assets in mortgage- and asset-backed securities, up to 10% of their
assets in zero coupon, pay-in-kind and step coupon securities, and without limit
in indexed/structured securities. No Growth Portfolio will invest 35% or more of
its assets in high-yield/high-risk securities.

Although Worldwide Growth Portfolio is committed to foreign investing, Growth
Portfolio and Aggressive Growth Portfolio

8 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

may also invest without limit in foreign equity and debt securities. The
Portfolios may invest directly in foreign securities denominated in a foreign
currency and not publicly traded in the United States. Other ways of investing
in foreign securities include depositary receipts or shares, and passive foreign
investment companies ("PFICs"). These Portfolios may use futures, options and
other derivatives for hedging purposes or for non-hedging purposes such as
seeking to enhance return. See "Additional Risk Factors" on page 13 for a
discussion of the risks associated with foreign investing and derivatives.

THE FOLLOWING QUESTIONS ARE DESIGNED TO HELP YOU BETTER UNDERSTAND AN INVESTMENT
IN THE GROWTH PORTFOLIOS.

Q: HOW ARE COMMON STOCKS SELECTED?

A: Each of these Portfolios invests substantially all of its assets in common
stocks to the extent the portfolio manager believes that the relevant
market environment favors profitable investing in those securities. Portfolio
managers generally take a "bottom up" approach to building their portfolios. In
other words, they seek to identify individual companies with earnings growth
potential that may not be recognized by the market at large. Although themes may
emerge in any Portfolio, securities are generally selected without regard to any
defined industry sector or other similarly defined selection procedure.
Realization of income is not a significant investment consideration. Any income
realized on these Portfolios' investments will be incidental to their
objectives.

Q: ARE THE SAME CRITERIA USED TO SELECT FOREIGN SECURITIES?

A: Generally, yes. Portfolio managers seek companies that meet their
selection criteria, regardless of country of organization or place of
principal business activity. Foreign securities are generally selected on a
stock-by-stock basis without regard to any defined allocation among countries or
geographic regions. However, certain factors such as expected levels of
inflation, government policies influencing business conditions, the outlook for
currency relationships, and prospects for economic growth among countries,
regions or geographic areas may warrant greater consideration in selecting
foreign securities. See "Additional Risk Factors" on page 13.

Q: WHAT IS THE MAIN RISK OF INVESTING IN A GROWTH PORTFOLIO?

A: Since the Growth Portfolios usually invest heavily in common stocks, the
fundamental risk is that the value of the stocks a Portfolio holds might
decrease. Stock values may fluctuate in response to the activities of an
individual company or in response to general market and economic conditions.
Historically, common stocks have provided greater long-term returns and have
entailed greater short-term risks than other investment choices. Smaller or
newer issuers are more likely to realize more substantial growth as well as
suffer more significant losses than larger or more established issuers.
Investments in such companies can be both more volatile and more speculative.
See "Additional Risk Factors" on page 13.

Q: WHAT IS MEANT BY "MARKET CAPITALIZATION"?

A: Market capitalization is the most commonly used measure of the size and
value of a company. It is computed by multiplying the current market price
of a share of the company's stock by the total number of its shares outstanding.
As noted previously, market capitalization is an important investment criteria
for Aggressive Growth Portfolio which may invest in small to medium sized
companies to a greater degree. Although Growth Portfolio and Worldwide Growth
Portfolio do not emphasize companies of any particular size, Portfolios with a
larger asset base are more likely to invest in larger, more-established issuers.

Q: HOW DOES A DIVERSIFIED PORTFOLIO DIFFER FROM A NONDIVERSIFIED PORTFOLIO?

A: Diversification is a means of reducing risk by investing a Portfolio's
assets in a broad range of stocks or other securities. A "nondiversified"
portfolio has the ability to take larger positions in a smaller number of
issuers. Because the appreciation or depreciation of a single stock may have a
greater impact on the share price of a nondiversified portfolio, its share price
can be expected to fluctuate more than a comparable diversified portfolio.
Aggressive Growth Portfolio is a nondiversified portfolio.

Q: HOW DO THESE PORTFOLIOS TRY TO REDUCE RISK?

A: Diversification of a Portfolio's assets reduces the effect of any single
holding on its overall portfolio value. A Portfolio may also use futures,
options and other derivative instruments to protect its portfolio from movements
in securities' prices and interest rates. The Portfolios may use a variety of
currency hedging techniques, including forward currency contracts, to manage
exchange rate risk when investing directly in foreign markets. See "Additional
Risk Factors" on page 13. In addition, to the extent that a Portfolio holds a
larger cash position, it may not participate in market declines to the same
extent as if the Portfolio remained more fully invested in common stocks.

BALANCED PORTFOLIO IS DESIGNED FOR INVESTORS WHO PRIMARILY SEEK GROWTH OF
CAPITAL INCLUDING AN EMPHASIS ON INCOME. IT IS NOT DESIGNED FOR INVESTORS WHO
DESIRE A CONSISTENT LEVEL OF INCOME.

Investment Objective:..........................................Growth of Capital
Including an Emphasis on Income
Primary Holdings:..............................................Common Stocks and
Income-Producing Securities
Shareholder's Investment Horizon:......................................Long-Term

BALANCED PORTFOLIO
The investment objective of this Portfolio is long-term capital growth,
consistent with preservation of capital and balanced by

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 9
<PAGE>

current income. It is a diversified Portfolio that, under normal circumstances,
pursues its objective by investing 40-60% of its assets in securities selected
primarily for their growth potential and 40-60% of its assets in securities
selected primarily for their income potential. This Portfolio normally invests
at least 25% of its assets in fixed-income senior securities, which include debt
securities and preferred stocks.

TYPES OF INVESTMENTS
Balanced Portfolio may invest in a combination of common stocks, preferred
stocks, convertible securities, debt securities and other fixed income
securities. Balanced Portfolio may invest in the types of investments previously
described under "Growth Portfolios" on page 8. The Portfolio may also invest in
the types of income-producing securities described for Flexible Income Portfolio
except that its investments in high-yield/high-risk securities will not exceed
35% of net assets and investments in mortgage- and asset-backed securities will
not exceed 25% of assets.

THE FOLLOWING QUESTIONS ARE DESIGNED TO HELP YOU BETTER UNDERSTAND AN INVESTMENT
IN BALANCED PORTFOLIO.

Q: HOW ARE ASSETS ALLOCATED BETWEEN THE GROWTH AND INCOME COMPONENTS OF
BALANCED PORTFOLIO?

A: Balanced Portfolio may shift assets between the growth and income
components of its portfolio based on the portfolio manager's analysis of
relevant market, financial and economic conditions. If the portfolio manager
believes that growth securities will provide better returns than the yields then
available or expected on income-producing securities, the Portfolio will place a
greater emphasis on the growth component.

Q: WHAT TYPES OF SECURITIES MAKE UP THE GROWTH COMPONENT OF BALANCED
PORTFOLIO?

A: The growth component of Balanced Portfolio is expected to consist
primarily of common stocks. The selection criteria for common stocks are
described on page 9. Because income is a part of the investment objective of
Balanced Portfolio, the portfolio manager may consider dividend-paying
characteristics to a greater degree in selecting equity securities. Balanced
Portfolio may also find opportunities for capital growth from debt securities
because of anticipated changes in interest rates, credit standing, currency
relationships or other factors.

Q: WHAT TYPES OF SECURITIES MAKE UP THE INCOME COMPONENT OF BALANCED
PORTFOLIO?

A: The income component of Balanced Portfolio will consist of securities that
the portfolio manager believes have income potential. Such securities may
include equity securities, convertible securities and all types of debt
securities. Equity securities may be included in the income component of
Balanced Portfolio if they currently pay dividends or a portfolio manager
believes they have potential for either increasing their dividends or commencing
dividends, if none are currently paid.

FLEXIBLE INCOME PORTFOLIO IS DESIGNED FOR THOSE INVESTORS WHO PRIMARILY SEEK
CURRENT INCOME.

Investment Objective:...............................................Total Return
Primary Holdings:....................................Income-Producing Securities
Shareholder's Investment Horizon:...............................Intermediate- to
Long-Term

FLEXIBLE INCOME PORTFOLIO
The investment objective of this Portfolio is to obtain maximum total return,
consistent with preservation of capital. The Portfolio pursues its objective
primarily through investments in income-producing securities. Total return is
expected to result from a combination of current income and capital
appreciation, although income will normally be the dominant component of total
return. As a fundamental policy, this Portfolio will invest at least 80% of its
assets in income-producing securities.

Flexible Income Portfolio may invest in a wide variety of income-producing
securities including corporate bonds and notes, government securities,
indexed/structured securities, preferred stock, income-producing common stocks,
debt securities that are convertible or exchangeable into equity securities, and
debt securities that carry with them the right to acquire equity securities as
evidenced by warrants attached to or acquired with the securities. The Portfolio
may invest to a lesser degree in common stocks, other equity securities or debt
securities that are not currently paying dividends or interest. The Portfolio
may purchase securities of any maturity and quality and the average maturity and
quality of its portfolio may vary substantially.

Flexible Income Portfolio may invest without limit in foreign securities,
including those of corporate and government issuers. The Portfolio may invest
without limit in high-yield/high-risk securities and may have substantial
holdings of such securities. The Portfolio may invest without limit in mortgage-
and asset-backed securities and in zero coupon, pay-in-kind and step coupon
securities. The risks of foreign securities and high-yield securities are
described under "Additional Risk Factors" on page 13.

The Portfolio may purchase defaulted debt securities if, in the opinion of Janus
Capital it appears likely that the issuer may resume interest payments or other
advantageous developments appear likely in the near term. Defaulted debt
securities may be illiquid and subject to the Portfolio's limit on illiquid
investments.

TYPES OF INVESTMENTS
In addition to the investment policies described above, Flexible Income
Portfolio may purchase securities on a when-issued, delayed delivery or forward
commitment basis. It may also use futures, options and other derivatives for
hedging purposes or for non-hedging purposes such as seeking to enhance return.
See "Additional Risk Factors" on page 13. When the portfolio manager is unable
to locate investment opportunities with

10 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

favorable risk/reward characteristics, the cash position of Flexible Income
Portfolio may increase and the Portfolio may have substantial holdings of cash
or cash equivalent short-term obligations. See "General Portfolio Policies" on
page 12.

THE FOLLOWING QUESTIONS ARE DESIGNED TO HELP YOU BETTER UNDERSTAND AN INVESTMENT
IN FLEXIBLE INCOME PORTFOLIO.
Q: HOW DO INTEREST RATES AFFECT THE VALUE OF MY INVESTMENT?
A: A fundamental risk associated with any fund that invests in fixed-income
securities (e.g., a bond fund) is the risk that the value of the
securities it holds will rise or fall as interest rates change. Generally, a
fixed-income security will increase in value when interest rates fall and
decrease in value when interest rates rise. Longer-term securities are generally
more sensitive to interest rate changes than shorter-term securities, but they
generally offer higher yields to compensate investors for the associated risks.
High-yield bond prices are generally less directly responsive to rate changes
than investment grade issues and may not always follow this pattern. A bond
fund's average-weighted effective maturity and its duration are measures of how
the portfolio may react to interest rate changes.
Q: WHAT IS MEANT BY A PORTFOLIO'S "AVERAGE-WEIGHTED EFFECTIVE MATURITY"?
A: The stated maturity of a bond is the date when the issuer must repay the
bond's entire principal value to an investor, such as a Portfolio. Some
types of bonds, such as mortgage-backed securities, which are subject to
prepayment risk, and securities with call provisions, may also have an
"effective maturity" that is shorter than the stated date. With respect to GNMA
securities and other mortgage-backed securities, effective maturity is likely to
be substantially less than the stated maturities of the mortgages in the
underlying pools. With respect to obligations with call provisions, effective
maturity is typically the next call date on which the obligation reasonably may
be expected to be called. Securities without prepayment or call provisions
generally have an effective maturity equal to their stated maturity.
Dollar-weighted effective maturity is calculated by averaging the effective
maturity of bonds held by a Portfolio with each effective maturity "weighted"
according to the percentage of net assets that it represents.

Q: WHAT IS MEANT BY A PORTFOLIO'S "DURATION"?

A: A bond's duration indicates the time it will take an investor to recoup
his or her investment. Unlike average maturity, duration reflects both
principal and interest payments. Generally, the higher the coupon rate on a
bond, the lower its duration will be. The duration of a bond fund is calculated
by averaging the duration of bonds held by a Portfolio with each duration
"weighted" according to the percentage of net assets that it represents. Because
duration accounts for interest payments, a Portfolio's duration is usually
shorter than its average maturity.

Q: HOW DOES FLEXIBLE INCOME PORTFOLIO MANAGE INTEREST RATE RISK?

A: The Portfolio may vary the average-weighted effective maturity to reflect
the portfolio manager's analysis of interest rate trends and other
factors. The Portfolio's average-weighted effective maturity will tend to be
shorter when the portfolio manager expects interest rates to rise and longer
when the portfolio manager expects interest rates to fall. The Portfolio may
also use futures, options and other derivatives to manage interest rate risk.
See "Additional Risk Factors" on page 13.

Q: WHAT IS MEANT BY "CREDIT QUALITY"?

A: Credit quality measures the likelihood that the issuer will meet its
obligations on a bond. One of the fundamental risks associated with all
bond funds is credit risk, which is the risk that an issuer will be unable to
make principal and interest payments when due. U.S. government securities are
generally considered to be the safest type of investment in terms of credit
risk. Municipal obligations generally rank between U.S. government securities
and corporate debt securities in terms of credit safety. Corporate debt
securities, particularly those rated below investment grade, present the highest
credit risk.

Q: HOW IS CREDIT QUALITY MEASURED?

A: Ratings published by nationally recognized rating agencies such as
Standard & Poor's Ratings Services ("Standard & Poor's") and Moody's
Investors Services, Inc. ("Moody's") are widely accepted measures of credit
risk. The lower a bond issue is rated by an agency, the more credit risk it is
considered to represent. Lower rated bonds generally pay higher yields to
compensate investors for the associated risk. Please refer to Appendix B for a
description of rating categories.

Q: WHAT IS A HIGH-YIELD/HIGH-RISK SECURITY?

A: A high-yield security (also called a "junk" bond) is a debt security rated
below investment grade by major rating agencies (i.e., BB or lower by
Standard & Poor's or Ba or lower by Moody's) or an unrated bond of similar
quality. It presents greater risk of default (the failure to make timely
interest and principal payments) than higher quality bonds.

Q: WHAT RISKS DO HIGH-YIELD/HIGH-RISK SECURITIES PRESENT?

A: High-yield securities are often considered to be more speculative and
involve greater risk of default or price changes due to changes in
economic and industry conditions and the issuer's creditworthiness. Their market
prices tend to fluctuate more than higher quality securities as a result of
changes in these factors.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 11
<PAGE>

The default rate of lower quality debt securities is likely to be higher when
issuers have difficulty meeting projected goals or obtaining additional
financing. This could occur during economic recessions or periods of high
interest rates. In addition, there may be a smaller market for lower quality
securities than for higher quality securities, making lower quality securities
more difficult to sell promptly at an acceptable price.

The junk bond market can experience sudden and sharp price swings. Because
Flexible Income Portfolio may invest a significant portion of its portfolio in
high-yield/high-risk securities, investors in the Portfolio should be willing to
tolerate a corresponding increase in the risk of significant and sudden changes
in NAV.

GENERAL PORTFOLIO POLICIES
Unless otherwise stated, each of the following policies applies to all of the
Portfolios. The percentage limitations included in these policies and elsewhere
in this Prospectus apply only at the time of purchase of the security. For
example, if a Portfolio exceeds a limit as a result of market fluctuations or
the sale of other securities, it will not be required to dispose of any
securities.

CASH POSITION
When a Portfolio's manager believes that market conditions are not favorable for
profitable investing or when the portfolio manager is otherwise unable to locate
favorable investment opportunities, a Portfolio's investments may be hedged to a
greater degree and/or its cash or similar investments may increase. In other
words, the Portfolios do not always stay fully invested in stocks and bonds.
Cash or similar investments are a residual - they represent the assets that
remain after a portfolio manager has committed available assets to desirable
investment opportunities. Partly because the portfolio managers act
independently of each other, the cash positions of the Portfolios may vary
significantly. Larger hedged positions and/or larger cash positions may serve as
a means of preserving capital in unfavorable market conditions.

Securities that the Portfolios may invest in as means of receiving a return on
idle cash include high-grade commercial paper, certificates of deposit,
repurchase agreements or other short-term debt obligations. The Portfolios may
also invest in money market funds (including funds managed by Janus Capital).
When a Portfolio is hedged or its investments in cash or similar investments
increase, it may not participate in stock or bond market advances or declines to
the same extent that it would if the Portfolio was not hedged or remained more
fully invested in stocks or bonds.

DIVERSIFICATION
The Investment Company Act of 1940 (the "1940 Act") classifies investment
companies as either diversified or nondiversified. All of the Portfolios (except
Aggressive Growth Portfolio) qualify as diversified funds under the 1940 Act,
and subject to the following diversification requirements:

- - As a fundamental policy, no Portfolio may own more than 10% of the outstanding
voting shares of any issuer.

- - As a fundamental policy, with respect to 50% of the total assets of Aggressive
Growth Portfolio and 75% of the total assets of the other Portfolios, no
Portfolio will purchase a security of any issuer (other than cash items and
U.S. government securities, as defined in the 1940 Act) if such purchase would
cause a Portfolio's holdings of that issuer to amount to more than 5% of that
Portfolio's total assets.

- - No Portfolio will invest more than 25% of its total assets in a single issuer
(other than U.S. government securities).

- - Aggressive Growth Portfolio reserves the right to become a diversified
portfolio by limiting the investments in which more than 5% of its total net
assets are invested.

INTERNAL REVENUE SERVICE (IRS) LIMITATIONS
In addition to the diversification requirements stated above, each Portfolio
intends to comply with the diversification requirements currently imposed by the
IRS on separate accounts of insurance companies as a condition of maintaining
the tax-deferred status of variable contracts. More specific information may be
contained in the participating insurance company's separate account prospectus.

INDUSTRY CONCENTRATION
As a fundamental policy, no Portfolio will invest 25% or more of its total
assets in any particular industry (excluding U.S. government securities).

PORTFOLIO TURNOVER
Each Portfolio generally intends to purchase securities for long-term investment
rather than short-term gains. However, short-term transactions may result from
liquidity needs, securities having reached a price or yield objective, changes
in interest rates or the credit standing of an issuer, or by reason of economic
or other developments not foreseen at the time of the initial investment
decision. Changes are made in a Portfolio whenever its portfolio manager
believes such changes are desirable. Portfolio turnover rates are generally not
a factor in making buy and sell decisions.

To a limited extent, a Portfolio may purchase securities in anticipation of
relatively short-term price gains. A Portfolio may also sell one security and
simultaneously purchase the same or comparable security to take advantage of
short-term differentials in bond yields or securities prices. Increased
portfolio turnover may result in higher costs for brokerage commissions, dealer
mark-ups and other transaction costs and may also result in taxable capital
gains.

12 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

of purchase, the Portfolio will take steps to reduce in an orderly fashion its
holdings of illiquid securities. An illiquid investment is a security or other
position that cannot be disposed of quickly in the normal course of business.
Some securities cannot be sold to the U.S. public because of their terms or
because of SEC regulations. Janus Capital will follow guidelines established by
the Trustees of the Trust ("Trustees") in making liquidity determinations for
Rule 144A securities and other securities, including privately placed commercial
paper and municipal lease obligations.

BORROWING AND LENDING
Each Portfolio may borrow money and lend securities or other assets, as follows:

- - Each Portfolio may borrow money for temporary or emergency purposes in amounts
up to 25% of its total assets.

- - Each Portfolio may mortgage or pledge securities as collateral for borrowings
in amounts up to 15% of its net assets.

- - As a fundamental policy, each Portfolio may lend securities or other assets
if, as a result, no more than 25% of its total assets would be lent to other
parties.

Under the terms of an exemptive order from the SEC, each Portfolio may borrow
money from or lend money to each other and other funds that permit such
transactions and for which Janus Capital serves as investment adviser. All such
borrowing and lending will be subject to the above percentage limits.

ADDITIONAL RISK FACTORS

FOREIGN SECURITIES
INVESTMENTS IN FOREIGN SECURITIES, INCLUDING THOSE OF FOREIGN GOVERNMENTS, MAY
INVOLVE GREATER RISKS THAN INVESTING IN COMPARABLE DOMESTIC SECURITIES.

Securities of some foreign companies and governments may be traded in the United
States, but many foreign securities are traded primarily in foreign markets. The
risks of foreign investing include:

- - CURRENCY RISK. A Portfolio may buy the local currency when it buys a foreign
currency denominated security and sell the local currency when it sells the
security. As long as a Portfolio holds a foreign security, its value will be
affected by the value of the local currency relative to the U.S. dollar. When
a Portfolio sells a foreign denominated security, its value may be worth less
in U.S. dollars even though the security increases in value in its home
country. U.S. dollar denominated securities of foreign issuers may also be
affected by currency risk.

- - POLITICAL AND ECONOMIC RISK. Foreign investments may be subject to heightened
political and economic risks, particularly in underdeveloped or developing
countries which may have relatively unstable governments and economies based
on only a few industries. In some countries, there is the risk that the
government may take over the assets or operations of a company or that the
government may impose taxes or limits on the removal of a Portfolio's assets
from that country. The Portfolios may invest in emerging market countries.
Emerging market countries involve greater risk such as immature economic
structures, national policies restricting investments by foreigners, and
different legal systems.

- - REGULATORY RISK. There may be less government supervision of foreign markets.
Foreign issuers may not be subject to the uniform accounting, auditing and
financial reporting standards and practices applicable to domestic issuers.
There may be less publicly available information about foreign issuers than
domestic issuers.

- - MARKET RISK. Foreign securities markets, particularly those of underdeveloped
or developing countries, may be less liquid and more volatile than domestic
markets. Certain markets may require payment for securities before delivery
and delays may be encountered in settling securities transactions. In some
foreign markets, there may not be protection against failure by other parties
to complete transactions. There may be limited legal recourse against an
issuer in the event of a default on a debt instrument.

- - TRANSACTION COSTS. Transaction costs of buying and selling foreign securities,
including brokerage, tax and custody costs, are generally higher than those
involved in domestic transactions.

Foreign securities purchased indirectly (e.g., depositary receipts) are subject
to many of the above risks, including currency risk, because their values depend
on the performance of a foreign security denominated in its home currency.

INVESTMENTS IN SMALLER COMPANIES
SMALLER OR NEWER COMPANIES MAY SUFFER MORE SIGNIFICANT LOSSES AS WELL AS REALIZE
MORE SUBSTANTIAL GROWTH THAN LARGER OR MORE ESTABLISHED ISSUERS.

Smaller or newer companies may lack depth of management, they may be unable to
generate funds necessary for growth or potential development, or they may be
developing or marketing new products or services for which markets are not yet
established and may never become established. In addition, such companies may be
insignificant factors in their industries and may be subject to intense
competition from larger or more established companies. Securities of smaller or
newer companies may have more limited trading markets than the markets for
securities of larger or more established issuers, and may be subject to wider
price fluctuations. Investments in such companies tend to be more volatile and
somewhat more speculative.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 13
<PAGE>

against potential adverse movements in securities prices, foreign currency
markets or interest rates. To a limited extent, the Portfolios may also use
derivative instruments for non-hedging purposes such as seeking to increase a
Portfolio's income or otherwise seeking to enhance return. Please refer to
Appendix A to this Prospectus and the SAI for a more detailed discussion of
these instruments.

The use of derivative instruments exposes the Portfolios to additional
investment risks and transaction costs. Risks inherent in the use of derivative
instruments include:

- - the risk that interest rates, securities prices and currency markets will not
move in the direction that a portfolio manager anticipates;

- - imperfect correlation between the price of derivative instruments and
movements in the prices of the securities, interest rates or currencies being
hedged;

- - the fact that skills needed to use these strategies are different from those
needed to select portfolio securities;

- - inability to close out certain hedged positions to avoid adverse tax
consequences;

- - the possible absence of a liquid secondary market for any particular
instrument and possible exchange-imposed price fluctuation limits, either of
which may make it difficult or impossible to close out a position when
desired;

- - leverage risk, that is, the risk that adverse price movements in an instrument
can result in a loss substantially greater than a Portfolio's initial
investment in that instrument (in some cases, the potential loss is
unlimited); and

- - particularly in the case of privately-negotiated instruments, the risk that
the counterparty will fail to perform its obligations, which could leave a
Portfolio worse off than if it had not entered into the position.

Although the Portfolios' managers believe the use of derivative instruments will
benefit the Portfolios, a Portfolio's performance could be worse than if the
Portfolio had not used such instruments if the portfolio manager's judgment
proves incorrect.

When a Portfolio invests in a derivative instrument, it may be required to
segregate cash and other liquid assets or certain portfolio securities with its
custodian to "cover" the Portfolio's position. Assets segregated or set aside
generally may not be disposed of so long as the Portfolio maintains the
positions requiring segregation or cover. Segregating assets could diminish the
Portfolio's return due to the opportunity losses of foregoing other potential
investments with the segregated assets.

HIGH-YIELD/HIGH-RISK SECURITIES
HIGH-YIELD/HIGH-RISK SECURITIES (OR "JUNK" BONDS) ARE DEBT SECURITIES RATED
BELOW INVESTMENT GRADE BY THE PRIMARY RATING AGENCIES (SUCH AS STANDARD & POOR'S
AND MOODY'S).

The value of lower quality securities generally is more dependent on the ability
of the issuer to meet interest and principal payments (i.e., credit risk) than
is the case for higher quality securities. Conversely, the value of higher
quality securities may be more sensitive to interest rate movements than lower
rated securities. Issuers of high-yield/high-risk securities may not be as
strong financially as those issuing bonds with higher credit ratings.
Investments in such companies are considered to be more speculative than higher
quality investments.

Issuers of high-yield/high-risk securities are more vulnerable to real or
perceived economic changes (for instance, an economic downturn or prolonged
period of rising interest rates), political changes or adverse developments
specific to the issuer. Adverse economic, political or other developments may
impair the issuer's ability to service principal and interest obligations, to
meet projected business goals and to obtain additional financing, particularly
if the issuer is highly leveraged. In the event of a default, a Portfolio would
experience a reduction of its income and could expect a decline in the market
value of the defaulted securities.

The market for lower quality securities is generally less liquid than the market
for higher quality securities. Adverse publicity and investor perceptions as
well as new or proposed laws may also have a greater negative impact on the
market for lower quality securities. Unrated debt, while not necessarily of
lower quality than rated securities, may not have as broad a market as higher
quality securities. Sovereign debt of foreign governments is generally rated by
country. Because these ratings do not take into account individual factors
relevant to each issue and may not be updated regularly, Janus Capital may treat
such securities as unrated debt.

The market prices of high-yield/high-risk securities structured as zero coupon
or pay-in-kind securities are generally affected to a greater extent by interest
rate changes and tend to be more volatile than securities which pay interest
periodically. In addition, zero coupon, pay-in-kind and delayed interest bonds
often do not pay interest until maturity. However, a Portfolio must recognize
imputed interest income and pay dividends to shareholders even though it has
received no cash. In some instances, the Portfolios may have to sell securities
to have sufficient cash to pay the dividends.

Please refer to Appendix B for a description of bond rating categories.

SHORT SALES
Each Portfolio may engage in "short sales against the box." This technique
involves selling either a security that a Portfolio owns, or a security
equivalent in kind and amount that a Portfolio has the right to obtain, for
delivery at a specified date in the future. A Portfolio may enter into a short
sale against the box to hedge against anticipated declines in the market price
of portfolio securities. If the value of the securities sold short increases
prior to the scheduled delivery date, the Portfolio loses the opportunity to
participate in the gain.

14 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

SPECIAL SITUATIONS
Each Portfolio may invest in "special situations" from time to time. A special
situation arises when, in the opinion of a Portfolio's manager, the securities
of a particular issuer will be recognized and appreciate in value due to a
specific development with respect to that issuer. Developments creating a
special situation might include, among others, a new product or process, a
technological breakthrough, a management change or other extraordinary corporate
event, or differences in market supply of and demand for the security.
Investment in special situations may carry an additional risk of loss in the
event that the anticipated development does not occur or does not attract the
expected attention.

See Appendix A for risks associated with certain other investments.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 15
<PAGE>

MANAGEMENT OF
THE PORTFOLIOS

TRUSTEES

The Trustees oversee the business affairs of the Trust and are responsible for
major decisions relating to each Portfolio's investment objective and policies.
The Trustees delegate the day-to-day management of the Portfolios to the
officers of the Trust and meet at least quarterly to review the Portfolios'
investment policies, performance, expenses and other business affairs.

INVESTMENT ADVISER
Janus Capital, 100 Fillmore Street, Denver, Colorado 80206-4928, is the
investment adviser to each of the Portfolios and is responsible for the
day-to-day management of the investment portfolios and other business affairs of
the Portfolios.

Janus Capital has served as investment adviser to Janus Fund since its inception
in 1970 and currently serves as investment adviser to all of the Janus retail
funds, as well as adviser or subadviser to other mutual funds and individual,
corporate, charitable and retirement accounts.

Kansas City Southern Industries, Inc. ("KCSI") owns approximately 83% of the
outstanding voting stock of Janus Capital, most of which it acquired in 1984.
KCSI is a publicly traded holding company whose primary subsidiaries are engaged
in transportation, information processing and financial services. Thomas H.
Bailey, President and Chairman of the Board of Janus Capital, owns approximately
12% of its voting stock and, by agreement with KCSI, selects a majority of Janus
Capital's Board.

Janus Capital furnishes continuous advice and recommendations concerning each
Portfolio's investments. Janus Capital also furnishes certain administrative,
compliance and accounting services for the Portfolios, and may be reimbursed by
the Portfolios for its costs in providing those services. In addition, Janus
Capital employees serve as officers of the Trust and Janus Capital provides
office space for the Portfolios and pays the salaries, fees and expenses of all
Portfolio officers and those Trustees who are affiliated with Janus Capital.

Participating insurance companies that purchase the Portfolios' Shares may
perform certain administrative services relating to the Portfolios and Janus
Capital or the Portfolios may pay those companies for such services.

INVESTMENT PERSONNEL
PORTFOLIO MANAGERS
JAMES P. CRAIG, III is Chief Investment Officer of Janus Capital. He is
Executive Vice President and portfolio manager of Growth Portfolio, which he has
managed since inception. Mr. Craig previously managed Balanced Portfolio from
September 1993 through April 1996. He has managed Janus Fund since 1986 and has
co-managed Janus Venture Fund since February 1, 1997. Mr. Craig previously
managed Janus Venture Fund from its inception to December 1993 and Janus
Balanced Fund from December 1993 to December 1995. He holds a Bachelor of Arts
in Business from the University of Alabama and a Master of Arts in Finance from
the Wharton School of the University of Pennsylvania.

JAMES P. GOFF is Executive Vice President and portfolio manager of Aggressive
Growth Portfolio which he has managed since inception. Mr. Goff joined Janus
Capital in 1988 and has managed Janus Enterprise Fund since its inception. Mr.
Goff co-managed or managed Janus Venture Fund from December 1993 to February 1,
1997. He holds a Bachelor of Arts in Economics from Yale University and is a
Chartered Financial Analyst.

HELEN YOUNG HAYES is Executive Vice President and portfolio manager of Worldwide
Growth Portfolio and co-manager of International Growth Portfolio which she has
managed or co-managed since inception. Ms. Hayes joined Janus Capital in 1987
and has managed or co-managed Janus Worldwide Fund and Janus Overseas Fund since
their inceptions. She holds a Bachelor of Arts in Economics from Yale University
and is a Chartered Financial Analyst.

BLAINE P. ROLLINS is Executive Vice President and portfolio manager of Balanced
Portfolio, which he has managed since May 1996 and Equity Income Portfolio which
he has managed since inception. He is an assistant portfolio manager of Growth
Portfolio. Mr. Rollins joined Janus Capital in 1990 and has managed Janus
Balanced Fund since January 1996 and Janus Equity Income Fund since June 1996.
He has been an assistant portfolio manager of Janus Fund since January 1995. He
gained experience as a fixed-income trader and equity research analyst prior to
managing Balanced Portfolio. He holds a Bachelor of Science in Finance from the
University of Colorado and is a Chartered Financial Analyst.

RONALD V. SPEAKER is Executive Vice President and portfolio manager of Flexible
Income Portfolio which he has managed or co-managed since its inception. He
previously served as co-manager of High-Yield Portfolio from its inception to
May 1998. He managed Short-Term Bond Portfolio from its inception through April
1996. Mr. Speaker joined Janus Capital in 1986. He has managed or co-managed
Janus Flexible Income Fund since December 1991 and previously managed both Janus
Short-Term Bond Fund and Janus Federal Tax-Exempt Fund from inception through
December 1995. He previously managed or co-managed Janus High-Yield Fund from
its inception to February 1998. He holds a Bachelor of Arts in Finance from the
University of Colorado and is a Chartered Financial Analyst.

In January 1997, Mr. Speaker settled an SEC administrative action involving two
personal trades made by him in January of 1993. Without admitting or denying the
allegations,

16 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

Mr. Speaker agreed to civil money penalty, disgorgement, and interest payments
totaling $37,199 and to a 90-day suspension which ended on April 25, 1997.

ASSISTANT PORTFOLIO MANAGERS
LAURENCE J. CHANG is assistant portfolio manager of Worldwide Growth Portfolio,
and co-manager of International Growth Portfolio. Mr. Chang also co-manages
Janus Overseas Fund and is assistant portfolio manager of Janus Worldwide Fund.
He received an undergraduate degree with honors in religion and philosophy from
Dartmouth College and a Master's Degree in Political Science from Stanford
University. He is a Chartered Financial Analyst.

DAVID C. DECKER is an assistant portfolio manager of Growth Portfolio. He is
also an assistant portfolio manager of Janus Fund. He is Executive Vice
President and portfolio manager of Janus Special Situations Fund. Mr. Decker
received a Masters of Business Administration in Finance from the Fuqua School
of Business at Duke University and a Bachelor's Degree in Economics and
Political Science from Tufts University. He is a Chartered Financial Analyst.

PERSONAL INVESTING
Janus Capital does not permit portfolio managers to purchase and sell securities
for their own accounts, except under the limited exceptions contained in Janus
Capital's policy governing personal investing. Janus Capital's policy requires
investment and other personnel to conduct their personal investment activities
in a manner that Janus Capital believes is not detrimental to the Portfolios or
Janus Capital's other advisory clients. See the SAI for more detailed
information.

MANAGEMENT EXPENSES AND EXPENSE LIMITS
Each Portfolio pays Janus Capital a management fee which is calculated daily.
The advisory agreement with each Portfolio spells out the management fee and
other expenses that the Portfolios must pay. Each of the Portfolios is subject
to the following management fee schedule (expressed as an annual rate):

<TABLE>
<CAPTION>
AVERAGE DAILY
NET ASSETS ANNUAL RATE EXPENSE LIMIT
FEE SCHEDULE OF PORTFOLIO PERCENTAGE(%) PERCENTAGE(%)
- --------------------------------------------------------------------------
<S> <C> <C> <C>
Growth, Aggressive First $300 Million 0.75 N/A(1)
Growth, Worldwide Next $200 Million 0.70
Growth and Over $500 Million 0.65
Balanced Portfolios
- --------------------------------------------------------------------------
Flexible Income First $300 Million 0.65 1.00(2)
Portfolio Over $300 Million 0.55
- --------------------------------------------------------------------------
</TABLE>

(1) Janus Capital has agreed to reduce Growth, Aggressive Growth, Worldwide
Growth and Balanced Portfolio's advisory fee to the extent that such fee
exceeds the effective rate of the Janus retail fund corresponding to such
Portfolio. Janus Capital may terminate this fee reduction any time upon at
least 90 days' notice to the Trustees. The effective rate is the advisory
fee calculated by the corresponding retail fund as of the last day of each
calendar quarter (expressed as an annual rate). The effective rates of
Janus Fund, Janus Enterprise Fund, Janus Worldwide Fund, and Janus
Balanced Fund were .65%, .72%, .65% and .73%, respectively, for the
quarter ended March 31, 1998.
(2) Janus Capital may terminate or modify the expense limitation at any time
upon at least 90 days' notice to the Trustees.

Differences in the actual management fees incurred by the Portfolios are due
primarily to variances in the asset sizes of the corresponding retail funds. As
asset size increases, the annual rate of the management fee rate declines in
accordance with the above schedule. In addition, the Shares of each Portfolio
incur expenses not assumed by Janus Capital, including transfer agent and
custodian fees and expenses, legal and auditing fees, printing and mailing costs
of sending reports and other information to existing shareholders, and
independent Trustees' fees and expenses. The fee schedule for the Growth,
Aggressive Growth, Worldwide Growth and Balanced Portfolios was effective July
1, 1997.

During the most recent fiscal year the Portfolios paid the following management
fees expressed as a percentage of average net assets: Growth Portfolio .65%;
Aggressive Growth Portfolio .73%; Worldwide Growth Portfolio .66%; and Balanced
Portfolio .76%.

PORTFOLIO TRANSACTIONS
Purchases and sales of securities on behalf of each Portfolio are executed by
broker-dealers selected by Janus Capital. Broker-dealers are selected on the
basis of their ability to obtain best price and execution for a Portfolio's
transactions and recognizing brokerage, research and other services provided to
the Portfolio and to Janus Capital. Janus Capital may consider sales of shares
of the Portfolios or other Janus funds by a broker-dealer or the recommendation
of a broker-dealer to its customers that they purchase a Portfolio's shares as a
factor in the selection of broker-dealers to execute portfolio transactions.
Janus Capital may also consider payments made by brokers effecting transactions
for a Portfolio i) to the Portfolio or ii) to other persons on behalf of the
Portfolio for services provided to the Portfolio for which it would be obligated
to pay. The Portfolios' Trustees have authorized Janus Capital to place
portfolio transactions on an agency basis with a broker-dealer affiliated with
Janus Capital. When transactions for a Portfolio are effected with that
broker-dealer, the commissions payable by the Portfolio are credited against
certain Portfolio operating expenses serving to reduce those expenses. The SAI
further explains the selection of broker-dealers.

OTHER SERVICE PROVIDERS
The following parties provide the Portfolios with administrative and other
services.

CUSTODIAN
State Street Bank and Trust Company
P.O. Box 0351
Boston, Massachusetts 02117-0351

TRANSFER AGENT
Janus Service Corporation
P.O. Box 173375
Denver, Colorado 80217-3375

Janus Service Corporation is a wholly-owned subsidiary of Janus Capital.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 17
<PAGE>

OTHER INFORMATION
ORGANIZATION
The Trust is a "mutual fund" that was organized as a Delaware business trust on
May 20, 1993. A mutual fund is an investment vehicle that pools money from
numerous investors and invests the money to achieve a specified objective. The
Trust consists of twelve separate series, five of which are offered by this
Prospectus.

Each Portfolio currently offers two classes of Shares, one of which, the
Institutional Shares, are offered pursuant to this prospectus and are sold under
the name Janus Aspen Series. The Shares offered by this Prospectus are available
only in connection with investment in and payments under variable insurance
contracts as well as certain qualified retirement plans. Retirement Shares of
each Portfolio are offered by separate prospectus and are available only to
participant directed qualified plans using plan service providers that are
compensated for providing distribution and/or recordkeeping and other
administrative services provided to plan participants. Because the expenses of
each class may differ, the performance of each class is expected to differ. If
you would like additional information about the Retirement Shares, please call
1-800-525-0020.

SHAREHOLDER MEETINGS AND VOTING RIGHTS
The Trust does not intend to hold annual shareholder meetings. However, special
meetings may be called for a specific class or Portfolio or for the Trust as a
whole for purposes such as electing or removing Trustees, terminating or
reorganizing the Trust, changing fundamental policies, or for any other purpose
requiring a shareholder vote under the 1940 Act. Separate votes are taken by
each class or Portfolio only if a matter affects or requires the vote of only
that class or Portfolio or the interest of a class or Portfolio in the matter
differs from the interest of the other class or Portfolios of the Trust. As a
shareholder, you are entitled to one vote for each share that you own.

An insurance company issuing a variable contract invested in Shares of a
Portfolio will request voting instructions from variable contract holders. Under
current law, the insurance company must vote all Shares held by the separate
account in proportion to the voting instructions received.

CONFLICTS OF INTEREST
Each Portfolio's Shares are available only to variable annuity and variable life
separate accounts of insurance companies that are unaffiliated with Janus
Capital and to certain qualified retirement plans. Retirement Shares of the
Portfolios (offered through a separate prospectus) are available to certain
participant directed qualified plans. Although the Portfolios do not currently
anticipate any disadvantages to policy owners arising out of the fact that each
Portfolio offers its shares to such entities, there is a possibility that a
material conflict may arise. The Trustees monitor events in order to identify
any anticipated disadvantages or material irreconcilable conflicts to determine
what action, if any, should be taken in response. If a material disadvantage or
conflict occurs, the Trustees may require one or more insurance company separate
accounts or plans to withdraw its investments in one or more Portfolios or
substitute shares of another Portfolio. If this occurs, a Portfolio may be
forced to sell securities at disadvantageous prices. In addition, the Trustees
may refuse to sell shares of any Portfolio to any separate account or may
suspend or terminate the offering of a Portfolio's shares if such action is
required by law or regulatory authority or is in the best interests of that
Portfolio's shareholders. It is possible that a qualified plan investing in the
Retirement Shares of the Portfolios could lose its qualified plan status under
the Internal Revenue Code, which could have adverse tax consequences on
insurance company separate accounts investing in the Shares. Janus Capital
intends to monitor such qualified plans and the Portfolios may discontinue sales
to a qualified plan and require plan participants with existing investments in
the Retirement Shares to redeem those investments if a plan loses (or in the
opinion of Janus Capital is at risk of losing) its qualified plan status.

MASTER/FEEDER OPTION
The Trust may in the future seek to achieve a Portfolio's investment objective
by investing all of that Portfolio's assets in another investment company having
the same investment objective and substantially the same investment policies and
restrictions as those applicable to that Portfolio. Unless otherwise required by
law, this policy may be implemented by the Trustees without shareholder
approval.

YEAR 2000
Preparing for Year 2000 is a high priority for Janus Capital, which has
established a dedicated group to address this issue. Janus Capital has entered
into a consulting arrangement with one of the foremost experts in Year 2000
compliance to help Janus Capital successfully achieve Year 2000 compliance.
Janus Capital does not anticipate that the move to Year 2000 will have a
material impact on its ability to continue to provide the Portfolios with
service at current levels.

THE VALUATION OF SHARES
The NAV of the Shares of a Portfolio is determined at the close of the regular
trading session of the New York Stock Exchange (the "NYSE") (normally 4:00 p.m.,
New York time) each day that the NYSE is open. NAV per share is determined by
dividing the total value of the securities and other assets, less liabilities,
by the total number of shares outstanding.

Securities are valued at market value or, if a market quotation is not readily
available, at their fair value determined in good faith under procedures
established by and under the supervision of the Trustees. Short-term instruments
maturing within 60 days are valued at amortized cost, which approximates market
value.

18 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

DISTRIBUTIONS AND TAXES

DISTRIBUTIONS
TO AVOID TAXATION OF THE PORTFOLIOS, THE INTERNAL REVENUE CODE REQUIRES EACH
PORTFOLIO TO DISTRIBUTE NET INCOME AND ANY NET GAINS REALIZED ON ITS INVESTMENTS
ANNUALLY. ORDINARY INCOME FROM DIVIDENDS AND INTEREST AND ANY NET REALIZED
SHORT-TERM CAPITAL GAINS ARE PAID TO SHAREHOLDERS AS ORDINARY INCOME DIVIDENDS.
NET REALIZED LONG-TERM GAINS, IF ANY, ARE PAID TO SHAREHOLDERS AS CAPITAL GAINS
DISTRIBUTIONS. EACH CLASS OF EACH PORTFOLIO MAKES SEMIANNUAL DISTRIBUTIONS IN
JUNE AND DECEMBER OF SUBSTANTIALLY ALL OF ITS INVESTMENT INCOME AND AN ANNUAL
DISTRIBUTION IN JUNE OF ITS NET REALIZED GAINS, IF ANY. ALL DIVIDENDS AND
CAPITAL GAINS DISTRIBUTIONS FROM THE SHARES OF A PORTFOLIO WILL BE AUTOMATICALLY
REINVESTED INTO ADDITIONAL SHARES OF THAT PORTFOLIO.

HOW DISTRIBUTIONS AFFECT NAV
Distributions are paid to shareholders as of the record date of the distribution
of a Portfolio, regardless of how long the shares have been held. Undistributed
income and realized gains are included in the daily NAV of a Portfolio's Shares.
The Share price of a Portfolio drops by the amount of the distribution, net of
any subsequent market fluctuations. For example, assume that on December 31, the
Shares of Growth Portfolio declared a dividend in the amount of $0.25 per share.
If the price of Growth Portfolio's Shares was $10.00 on December 30, the Share
price on December 31 would be $9.75, barring market fluctuations.

TAXES
TAXES ON DISTRIBUTIONS
Because Shares of the Portfolios may be purchased only through variable
insurance contracts and qualified plans, it is anticipated that any income
dividends or capital gains distributions made by the Shares of a Portfolio will
be exempt from current taxation if left to accumulate within the variable
insurance contract or qualified plan. Generally, withdrawals from such contracts
may be subject to ordinary income tax and, if made before age 59 1/2, a 10%
penalty tax. The tax status of your investment in the Shares depends on the
features of the variable insurance contracts purchased from a participating
insurance company. Further information may be found in the prospectus of the
separate account offering such contract.

TAXATION OF THE PORTFOLIOS
Dividends, interest and some gains received by the Portfolios on foreign
securities may be subject to withholding of foreign taxes. The Portfolios may
from year to year make the election permitted under section 853 of the Internal
Revenue Code to pass through such taxes to shareholders as a foreign tax credit.
If such an election is not made, any foreign taxes paid or accrued will
represent an expense to the Portfolios which will reduce their investment
income.

The Portfolios do not expect to pay any federal income or excise taxes because
they intend to meet certain requirements of the Internal Revenue Code. In
addition, each Portfolio intends to qualify under the Internal Revenue Code with
respect to the diversification requirements related to the tax-deferred status
of insurance company separate accounts.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 19
<PAGE>

SHAREHOLDER'S GUIDE

INVESTORS MAY NOT PURCHASE OR REDEEM SHARES OF THE PORTFOLIOS DIRECTLY. SHARES
MAY BE PURCHASED OR REDEEMED ONLY THROUGH VARIABLE INSURANCE CONTRACTS OFFERED
BY THE SEPARATE ACCOUNTS OF PARTICIPATING INSURANCE COMPANIES OR THROUGH
QUALIFIED RETIREMENT PLANS. REFER TO THE PROSPECTUS FOR THE PARTICIPATING
INSURANCE COMPANY'S SEPARATE ACCOUNT OR YOUR PLAN DOCUMENTS FOR INSTRUCTIONS ON
PURCHASING OR SELLING OF VARIABLE INSURANCE CONTRACTS AND ON HOW TO SELECT
SPECIFIC PORTFOLIOS AS INVESTMENT OPTIONS FOR A CONTRACT OR A QUALIFIED PLAN.

PURCHASES
Purchases of Shares may be made only by the separate accounts of insurance
companies for the purpose of funding variable insurance contracts or by
qualified plans. Refer to the prospectus of the appropriate insurance company
separate account or your plan documents for information on how to invest in the
Shares of each Portfolio.

All investments in the Portfolios are credited to a participating insurance
company's separate account or a qualified plan immediately upon acceptance of
the investment by a Portfolio. Investments will be processed at the NAV next
determined after an order is received and accepted by a Portfolio.

Each Portfolio reserves the right to reject any specific purchase order.
Purchase orders may be refused if, in Janus Capital's opinion, they are of a
size that would disrupt the management of a Portfolio. Any Portfolio may
discontinue sales of its shares if management believes that a substantial
further increase may adversely affect that Portfolio's ability to achieve its
investment objective. In such event, however, it is anticipated that existing
policy owners and plan participants invested in that Portfolio would be
permitted to continue to authorize investment in such Portfolio and to reinvest
any dividends or capital gains distributions.

REDEMPTIONS
Redemptions, like purchases, may be effected only through the separate accounts
of participating insurance companies or through qualified plans. Please refer to
the appropriate separate account prospectus or plan documents for details.

Shares of any Portfolio may be redeemed on any business day. Redemptions are
processed at the NAV next calculated after receipt and acceptance of the
redemption order by the Portfolio. Redemption proceeds will normally be wired to
the participating insurance company the business day following receipt of the
redemption order, but in no event later than seven days after receipt of such
order.

SHAREHOLDER COMMUNICATIONS
Shareholders will receive annual and semiannual reports including the financial
statements of the Shares of the Portfolios that they have authorized for
investment. Each report will show the investments owned by each Portfolio and
the market values thereof, as well as other information about the Portfolios and
their operations. The Trust's fiscal year ends December 31.

20 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

APPENDIX A

GLOSSARY OF INVESTMENT TERMS

This glossary provides a more detailed description of some of the types of
securities and other instruments in which the Portfolios may invest. The
Portfolios may invest in these instruments to the extent permitted by their
investment objective and policies. The Portfolios are not limited by this
discussion and may invest in any other types of instruments not precluded by the
policies discussed elsewhere in this Prospectus. Please refer to the SAI for a
more detailed discussion of certain instruments.

I. EQUITY AND DEBT SECURITIES
BONDS are debt securities issued by a company, municipality, government or
government agency. The issuer of a bond is required to pay the holder the amount
of the loan (or par value of the bond) at a specified maturity and to make
scheduled interest payments.

COMMERCIAL PAPER is a short-term debt obligation with a maturity ranging from 1
to 270 days issued by banks, corporations and other borrowers to investors
seeking to invest idle cash. The Portfolios may purchase commercial paper issued
under Section 4(2) of the Securities Act of 1933.

COMMON STOCK represents a share of ownership in a company and usually carries
voting rights and earns dividends. Unlike preferred stock, dividends on common
stock are not fixed but are declared at the discretion of the issuer's board of
directors.

CONVERTIBLE SECURITIES are preferred stocks or bonds that pay a fixed dividend
or interest payment and are convertible into common stock at a specified price
or conversion ratio.

DEPOSITARY RECEIPTS are receipts for shares of a foreign-based corporation that
entitle the holder to dividends and capital gains on the underlying security.
Receipts include those issued by domestic banks (American Depositary Receipts),
foreign banks (Global or European Depositary Receipts) and broker-dealers
(depositary shares).

FIXED-INCOME SECURITIES are securities that pay a specified rate of return. The
term generally includes short- and long-term government, corporate and municipal
obligations that pay a specified rate of interest or coupons for a specified
period of time and preferred stock, which pays fixed dividends. Coupon and
dividend rates may be fixed for the life of the issue or, in the case of
adjustable and floating rate securities, for a shorter period.

HIGH-YIELD/HIGH-RISK SECURITIES are securities that are rated below investment
grade by the primary rating agencies (e.g., BB or lower by Standard & Poor's and
Ba or lower by Moody's). Other terms commonly used to describe such securities
include "lower rated bonds," "noninvestment grade bonds" and "junk bonds."

MORTGAGE- AND ASSET-BACKED securities are shares in a pool of mortgages or other
debt. These securities are generally pass-through securities, which means that
principal and interest payments on the underlying securities (less servicing
fees) are passed through to shareholders on a pro rata basis. These securities
involve prepayment risk, which is the risk that the underlying mortgages or
other debt may be refinanced or paid off prior to their maturities during
periods of declining interest rates. In that case, a portfolio manager may have
to reinvest the proceeds from the securities at a lower rate. Potential market
gains on a security subject to prepayment risk may be more limited than
potential market gains on a comparable security that is not subject to
prepayment risk.

PASSIVE FOREIGN INVESTMENT COMPANIES (PFICS) are any foreign corporations which
generate certain amounts of passive income or hold certain amounts of assets for
the production of passive income. Passive income includes dividends, interest,
royalties, rents and annuities. To avoid taxes and interest that the Portfolios
must pay if these investments are profitable, the Portfolios may make various
elections permitted by the tax laws. These elections could require that the
Portfolios recognize taxable income, which in turn must be distributed, before
the securities are sold and before cash is received to pay the distributions.

PAY-IN-KIND BONDS are debt securities that normally give the issuer an option to
pay cash at a coupon payment date or give the holder of the security a similar
bond with the same coupon rate and a face value equal to the amount of the
coupon payment that would have been made.

REPURCHASE AGREEMENTS involve the purchase of a security by a Portfolio and a
simultaneous agreement by the seller (generally a bank or dealer) to repurchase
the security from the Portfolio at a specified date or upon demand. This
technique offers a method of earning income on idle cash. These securities
involve the risk that the seller will fail to repurchase the security, as
agreed. In that case, a Portfolio will bear the risk of market value
fluctuations until the security can be sold and may encounter delays and incur
costs in liquidating the security.

REVERSE REPURCHASE AGREEMENTS involve the sale of a security by a Portfolio to
another party (generally a bank or dealer) in return for cash and an agreement
by the Portfolio to buy the security back at a specified price and time. This
technique will be used to provide cash to satisfy unusually high redemption
requests or for other temporary or emergency purposes.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 21
<PAGE>

RULE 144A SECURITIES are securities that are not registered for sale to the
general public under the Securities Act of 1933, but that may be resold to
certain institutional investors.

STANDBY COMMITMENTS are obligations purchased by a Portfolio from a dealer that
give the Portfolio the option to sell a security to the dealer at a specified
price.

STEP COUPON BONDS are debt securities that trade at a discount from their face
value and pay coupon interest. The discount from the face value depends on the
time remaining until cash payments begin, prevailing interest rates, liquidity
of the security and the perceived credit quality of the issuer.

STRIP BONDS are debt securities that are stripped of their interest (usually by
a financial intermediary) after the securities are issued. The market value of
these securities generally fluctuates more in response to changes in interest
rates than interest-paying securities of comparable maturity.

TENDER OPTION BONDS are generally long-term securities that are coupled with an
option to tender the securities to a bank, broker-dealer or other financial
institution at periodic intervals and receive the face value of the bond. This
type of security is commonly used as a means of enhancing the security's
liquidity.

U.S. GOVERNMENT SECURITIES include direct obligations of the U.S. government
that are supported by its full faith and credit. Treasury bills have initial
maturities of less than one year, Treasury notes have initial maturities of one
to ten years and Treasury bonds may be issued with any maturity but generally
have maturities of at least ten years. U.S. government securities also include
indirect obligations of the U.S. government that are issued by federal agencies
and government sponsored entities. Unlike Treasury securities, agency securities
generally are not backed by the full faith and credit of the U.S. government.
Some agency securities are supported by the right of the issuer to borrow from
the Treasury, others are supported by the discretionary authority of the U.S.
government to purchase the agency's obligations and others are supported only by
the credit of the sponsoring agency.

VARIABLE AND FLOATING RATE SECURITIES have variable or floating rates of
interest and, under certain limited circumstances, may have varying principal
amounts. These securities pay interest at rates that are adjusted periodically
according to a specified formula, usually with reference to some interest rate
index or market interest rate. The floating rate tends to decrease the
security's price sensitivity to changes in interest rates.

WARRANTS are securities, typically issued with preferred stock or bonds, that
give the holder the right to buy a proportionate amount of common stock at a
specified price, usually at a price that is higher than the market price at the
time of issuance of the warrant. The right may last for a period of years or
indefinitely.

WHEN-ISSUED, DELAYED DELIVERY AND FORWARD TRANSACTIONS generally involve the
purchase of a security with payment and delivery at some time in the
future - i.e., beyond normal settlement. The Portfolios do not earn interest on
such securities until settlement and bear the risk of market value fluctuations
between the purchase and settlement dates. New issues of stocks and bonds,
private placements and U.S. government securities may be sold in this manner.

ZERO COUPON BONDS are debt securities that do not pay interest at regular
intervals, but are issued at a discount from face value. The discount
approximates the total amount of interest the security will accrue from the date
of issuance to maturity. The market value of these securities generally
fluctuates more in response to changes in interest rates than interest-paying
securities of comparable securities.

II. FUTURES, OPTIONS
AND OTHER DERIVATIVES
FORWARD CONTRACTS are contracts to purchase or sell a specified amount of a
financial instrument for an agreed upon price at a specified time. Forward
contracts are not currently exchange traded and are typically negotiated on an
individual basis. The Portfolios may enter into forward currency contracts to
hedge against declines in the value of non-dollar denominated securities or to
reduce the impact of currency appreciation on purchases of non-dollar
denominated securities. They may also enter into forward contracts to purchase
or sell securities or other financial indices.

FUTURES CONTRACTS are contracts that obligate the buyer to receive and the
seller to deliver an instrument or money at a specified price on a specified
date. The Portfolios may buy and sell futures contracts on foreign currencies,
securities and financial indices including interest rates or an index of U.S.
government, foreign government, equity or fixed-income securities. The
Portfolios may also buy options on futures contracts. An option on a futures
contract gives the buyer the right, but not the obligation, to buy or sell a
futures contract at a specified price on or before a specified date. Futures
contracts and options on futures are standardized and traded on designated
exchanges.

INDEXED/STRUCTURED SECURITIES are typically short- to intermediate-term debt
securities whose value at maturity or interest rate is linked to currencies,
interest rates, equity securities, indices, commodity prices or other financial
indicators. Such securities may be positively or negatively indexed (i.e., their
value may increase or decrease if the reference index or instrument
appreciates). Indexed/structured securities may have return characteristics
similar to direct investments in the underlying instruments and may be more
volatile than the underlying instruments. A Portfolio bears the market risk of
an investment in the underlying instruments, as well as the credit risk of the
issuer.

INTEREST RATE SWAPS involve the exchange by two parties of their respective
commitments to pay or receive interest (e.g., an exchange of floating rate
payments for fixed rate payments).

INVERSE FLOATERS are debt instruments whose interest rate bears an inverse
relationship to the interest rate on another

22 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

instrument or index. For example, upon reset the interest rate payable on a
security may go down when the underlying index has risen. Certain inverse
floaters may have an interest rate reset mechanism that multiplies the effects
of change in the underlying index. Such mechanism may increase the volatility of
the security's market value.

OPTIONS are the right, but not the obligation, to buy or sell a specified amount
of securities or other assets on or before a fixed date at a predetermined
price. The Portfolios may purchase and write put and call options on securities,
securities indices and foreign currencies.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 23
<PAGE>

APPENDIX B

EXPLANATION OF RATING CATEGORIES
The following is a description of credit ratings issued by two of the major
credit ratings agencies. Credit ratings evaluate only the safety of principal
and interest payments, not the market value risk of lower quality securities.
Credit rating agencies may fail to change credit ratings to reflect subsequent
events on a timely basis. Although the adviser considers security ratings when
making investment decisions, it also performs its own investment analysis and
does not rely solely on the ratings assigned by credit agencies.

STANDARD & POOR'S RATINGS SERVICES

<TABLE>
<CAPTION>
BOND RATING EXPLANATION
- --------------------------------------------------------------
<S> <C>
INVESTMENT GRADE
AAA Highest rating; extremely strong
capacity to pay principal and interest.
AA High quality; very strong capacity to
pay principal and interest.
A Strong capacity to pay principal and
interest; somewhat more susceptible to
the adverse effects of changing
circumstances and economic conditions.
BBB Adequate capacity to pay principal and
interest; normally exhibit adequate
protection parameters, but adverse
economic conditions or changing
circumstances more likely to lead to a
weakened capacity to pay principal and
interest than for higher rated bonds.
NON-INVESTMENT GRADE
BB, B, CCC, CC, C Predominantly speculative with respect
to the issuer's capacity to meet
required interest and principal
payments. BB - lowest degree of
speculation; C - the highest degree of
speculation. Quality and protective
characteristics outweighed by large
uncertainties or major risk exposure to
adverse conditions.
D In default.
- --------------------------------------------------------------
</TABLE>

MOODY'S INVESTORS SERVICE, INC.

<TABLE>
<S> <C>
INVESTMENT GRADE
Aaa Highest quality, smallest degree of
investment risk.
Aa High quality; together with Aaa bonds,
they compose the high-grade bond group.
A Upper-medium grade obligations; many
favorable investment attributes.
Baa Medium-grade obligations; neither highly
protected nor poorly secured. Interest
and principal appear adequate for the
present but certain protective elements
may be lacking or may be unreliable over
any great length of time.
NON-INVESTMENT GRADE
Ba More uncertain, with speculative
elements. Protection of interest and
principal payments not Well safeguarded
during good and bad times.
B Lack characteristics of desirable
investment; potentially low assurance of
timely interest and principal payments
or maintenance of other contract terms
over time.
Caa Poor standing, may be in default;
elements of danger with respect to
principal or interest payments.
Ca Speculative in a high degree; could be
in default or have other marked
shortcomings.
C Lowest-rated; extremely poor prospects
of ever attaining investment standing.
- --------------------------------------------------------------
</TABLE>

* Unrated securities are treated as noninvestment grade unless the portfolio
manager determines that such securities are the equivalent of investment grade
securities. Split rated securities may be treated as investment grade so long
as at least one major agency has rated the security as investment grade.

SECURITIES HOLDINGS BY RATING CATEGORY
During the fiscal year ended December 31, 1997, the percentage of securities
holdings for the Flexible Income Portfolio by rating category based upon a
weighted monthly average was:

<TABLE>
<CAPTION>
FLEXIBLE INCOME
BONDS - S&P RATING PORTFOLIO
<S> <C>
AAA 21%
AA 0%
A 15%
BBB 12%
BB 11%
B 27%
CCC 1%
CC 0%
C 0%
Preferred Stock 2%
Cash and Options 11%
- ------------------------------------
TOTAL 100%
- ------------------------------------
</TABLE>

No other Portfolio held 5% or more of its assets in bonds rated below investment
grade for the fiscal year ended December 31, 1997.

24 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>
JANUS ASPEN SERIES
PROSPECTUS
Growth Portfolio
Aggressive Growth Portfolio
Worldwide Growth Portfolio
Balanced Portfolio
Flexible Income Portfolio

[JANUS LOGO]

P.O. Box 173375 o Denver, CO 80217-3375 o 1-800-525-3713
(5/98)

<PAGE>

JANUS ASPEN SERIES

Prospectus

MAY 1, 1998

This prospectus describes two mutual funds, each of which has its own investment
objective and policies (the "Portfolios"). Each Portfolio is a series of Janus
Aspen Series (the "Trust") and currently offers two classes of shares. The
Institutional Shares are sold under the name "Janus Aspen Series." The Trust is
registered with the Securities and Exchange Commission ("SEC") as an open-end
management investment company. The Institutional Shares of each Portfolio
(collectively, the "Shares") are offered by this prospectus in connection with
investment in and payments under variable annuity contracts and variable life
insurance contracts (collectively "variable insurance contracts"), as well as
certain qualified retirement plans. Janus Capital Corporation ("Janus Capital")
serves as investment adviser to each Portfolio. Janus Capital has been in the
investment advisory business for over 27 years and currently manages
approximately $80 billion in assets.

The Trust sells and redeems its shares at net asset value without any sales
charges, commissions or redemption fees. Each variable insurance contract
involves fees and expenses not described in this Prospectus. See the
accompanying contract prospectus for information regarding contract fees and
expenses and any restrictions on purchases or allocations.

THESE SECURITIES HAVE NOT BEEN APPROVED BY THE SEC NOR HAS THE SEC PASSED ON THE
ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A
CRIMINAL OFFENSE.

THIS PROSPECTUS DOES NOT CONSTITUTE AN OFFER TO SELL SECURITIES IN ANY STATE OR
OTHER JURISDICTION TO ANY PERSON TO WHOM IT IS UNLAWFUL TO MAKE SUCH AN OFFER IN
SUCH STATE OR OTHER JURISDICTION.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

CONTENTS

<TABLE>
<S> <C>
THE PORTFOLIOS AT A GLANCE
Brief description of the Portfolios......................... 2
EXPENSE INFORMATION
Each Portfolio's annual operating expenses.................. 3
Financial Highlights -- a summary of financial data......... 4
PERFORMANCE TERMS
An explanation of performance terms......................... 6
THE PORTFOLIOS IN DETAIL
Investment Objectives and Policies.......................... 7
General Portfolio Policies.................................. 9
Additional Risk Factors..................................... 10
MANAGEMENT OF THE PORTFOLIOS
Investment Adviser and Investment Personnel................. 13
Personal Investing.......................................... 13
Management Expenses......................................... 13
Portfolio Transactions...................................... 14
Other Service Providers..................................... 14
Other Information........................................... 14
DISTRIBUTIONS AND TAXES
Distributions............................................... 16
Taxes....................................................... 16
SHAREHOLDER'S GUIDE
Purchases................................................... 17
Redemptions................................................. 17
Shareholder Communications.................................. 17
APPENDIX A.................................................. 18
Glossary of Investment Terms................................ 18
</TABLE>

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 1
<PAGE>

PORTFOLIOS AT A GLANCE

2 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

EXPENSE INFORMATION

SHAREHOLDER TRANSACTION EXPENSES (applicable to each Portfolio)

ANNUAL OPERATING EXPENSES (after fee and reductions)(1)
(expressed as a percentage of average net assets)

<TABLE>
<CAPTION>
- ------------------------------------------------------------------------------------------------------------------
MANAGEMENT TOTAL OPERATING
FEE OTHER EXPENSES EXPENSES
- ------------------------------------------------------------------------------------------------------------------
<S> <C> <C> <C>

Worldwide Growth Portfolio 0.66% 0.08% 0.74%
Balanced Portfolio 0.76% 0.07% 0.83%
-----------------------------------------------------------------------------------------------------------------
</TABLE>

(1) Management fees for Worldwide Growth and Balanced Portfolios reflect a
reduced fee schedule effective July 1, 1997. The management fee for each of
these Portfolios reflects the new rate applied to net assets as of December
31, 1997. Other expenses are based on the gross expenses of the Shares
before expense offset arrangements for the fiscal year ended December 31,
1997. The information for each Portfolio is net of fee reductions from Janus
Capital. Fee reductions for Worldwide Growth and Balanced Portfolios reduce
the management fee to the level of the corresponding Janus retail fund.
Without such reductions, the Management Fee, Other Expenses and Total
Operating Expenses would have been 0.72%, 0.09%, and 0.81% for the Worldwide
Growth Portfolio; and 0.77%, 0.06% and 0.83% for Balanced Portfolio,
respectively. Janus Capital may modify or terminate the reductions at any
time upon at least 90 days' notice to the Trustees.

EXAMPLE

<TABLE>
<CAPTION>
- ----------------------------------------------------------------------------------------------------------------
1 YEAR 3 YEARS 5 YEARS 10 YEARS
- ----------------------------------------------------------------------------------------------------------------
<S> <C> <C> <C> <C>

Worldwide Growth Portfolio $8 $24 $41 $ 92
Balanced Portfolio $8 $26 $46 $103
---------------------------------------------------------------------------------------------------------------
</TABLE>

THE EXAMPLE SHOULD NOT BE CONSIDERED A REPRESENTATION OF PAST OR FUTURE RETURNS
OR EXPENSES WHICH MAY BE MORE OR LESS THAN THOSE SHOWN.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 3
<PAGE>

FINANCIAL HIGHLIGHTS

Unless otherwise noted, the information below is for fiscal periods ending on
December 31st of each year. The accounting firm of Price Waterhouse LLP has
audited the Portfolios' financial statements since their inception. Their report
is included in the Portfolios' Annual Report, which is incorporated by reference
into the SAI. A DETAILED EXPLANATION OF THE FINANCIAL HIGHLIGHTS CAN BE FOUND ON
PAGE 5.
<TABLE>
<CAPTION>
WORLDWIDE GROWTH PORTFOLIO
INSTITUTIONAL SHARES 1997 1996 1995 1994 1993(1)
- -------------------------------------------------------------------------------------------------------
<C> <S> <C> <C> <C> <C> <C>
1. Net asset value, beginning of
period 19.44 $15.31 $12.07 $11.89 $10.00
- -------------------------------------------------------------------------------------------------------
INCOME FROM INVESTMENT OPERATIONS:
2. Net investment income .16 .16 .11 .04 .02
3. Net gains or (losses) on
securities (both realized and
unrealized) 4.14 4.27 3.19 .14 1.89
- -------------------------------------------------------------------------------------------------------
4. Total from investment operations 4.30 4.43 3.30 .18 1.91
- -------------------------------------------------------------------------------------------------------
LESS DISTRIBUTIONS:
5. Dividends (from net investment
income) (.17) (.17) (.06) -- (.01)
6. Dividends (in excess of net
investment income) (.02) -- -- -- --
7. Tax return of capital
distributions -- -- -- -- --
8. Distributions (from capital gains) (.16) (.13) -- -- (.01)
- -------------------------------------------------------------------------------------------------------
9. Total distributions (.35) (.30) (.06) -- (.02)
- -------------------------------------------------------------------------------------------------------
10. Net asset value, end of period $23.39 $19.44 $15.31 $12.07 $11.89
- -------------------------------------------------------------------------------------------------------
11. Total return* 22.15% 29.04% 27.37% 1.53% 19.10%
- -------------------------------------------------------------------------------------------------------
12. Net assets, end of period (in
thousands) $1,576,548 $582,603 $108,563 $37,728 $4,856
13. Average net assets for the period
(in thousands) $1,148,951 $304,111 $59,440 $22,896 $2,200
14. Ratio of gross expenses to average
net assets** 0.74%(7) 0.80%(6) 0.90%(5) N/A N/A
15. Ratio of net expenses to average
net assets** 0.74% 0.80% 0.87% 1.18%(2)(4) 0.25%(3)
16. Ratio of net investment income to
average net assets** 0.67% 0.83% 0.95% 0.50% 0.84%
17. Portfolio turnover rate** 80% 62% 113% 217% 57%
18. Average commission rate $0.0337 $0.0345 N/A N/A N/A
- -------------------------------------------------------------------------------------------------------

<CAPTION>
BALANCED PORTFOLIO
1997 1996 1995 1994 1993(1)

<C> <C> <C> <C> <C> <C>
1.
14.77 $13.03 $10.63 $10.64 $10.00
- ----------------------------------------------------------------

2. .34 .32 .17 .15 .08
3.

2.89 1.81 2.45 (.06) .64
- ----------------------------------------------------------------
4. 3.23 2.13 2.62 .09 .72
- ----------------------------------------------------------------

5.
(.35) (.30) (.22) (.10) (.08)
6.
-- -- -- -- --
7.
-- -- -- -- --
8. (.18) (.09) -- -- --
- ----------------------------------------------------------------
9. (.53) (.39) (.22) (.10) (.08)
- ----------------------------------------------------------------
10. $17.47 $14.77 $13.03 $10.63 $10.64
- ----------------------------------------------------------------
11. 22.10% 16.18% 24.79% 0.84% 7.20%
- ----------------------------------------------------------------
12.
$362,409 $85,480 $14,021 $3,153 $537
13.
$176,432 $43,414 $5,739 $2,336 $521
14.
0.83%(7) 0.94%(6) 1.37%(5) N/A N/A
15.
0.82% 0.92% 1.30% 1.57%(2)(4) 0.25%(3)
16.
2.87% 2.92% 2.41% 1.90% 2.69%
17. 139% 103% 149% 158% 126%
18. $0.0456 $0.0426 N/A N/A N/A
- ----------------------------------------------------------------
</TABLE>

* Total return not annualized for periods of less than one year.
** Annualized for periods of less than one full year.
(1) September 13, 1993 (inception) to December 31, 1993.
(2) Commissions payable by the Portfolio for transactions effected by a
broker-dealer affiliated with Janus Capital were credited against the
Portfolio's operating expenses. The effect of such directed brokerage
arrangement was de minimis.
(3) The ratio was 2.71% and 7.92%, respectively, for Worldwide Growth Portfolio
and Balanced Portfolio before waiver of certain fees and/or voluntary
reduction of adviser's fees to the effective rate of the corresponding Janus
retail fund.
(4) The ratio was 1.49% and 1.74%, respectively, for Worldwide Growth Portfolio
and Balanced Portfolio before voluntary reduction of adviser's fees to the
effective rate of the corresponding Janus retail fund.
(5) The ratio was 1.09% and 1.55%, respectively, for Worldwide Growth Portfolio
and Balanced Portfolio before voluntary reduction of adviser's fees to the
effective rate of the corresponding Janus retail fund.
(6) The ratio was 0.91% and 1.07%, respectively, for Worldwide Growth Portfolio
and Balanced Portfolio before voluntary reduction of adviser's fees to the
effective rate of the corresponding Janus retail fund.
(7) The ratio was 0.81% and 0.83%, respectively, for Worldwide Growth Portfolio
and Balanced Portfolio before voluntary reduction of adviser's fees to the
effective rate of the corresponding Janus retail fund.

4 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

UNDERSTANDING THE
FINANCIAL HIGHLIGHTS

This section is designed to help you better understand the information
summarized in the Financial Highlights table. The table contains important
historical operating information that may be useful in making your investment
decision or understanding how your investment has performed. The Portfolio's
Annual Report contains additional information about the Portfolio's performance,
including a comparison to an appropriate securities index. To request a copy of
the Annual Report, please call or write your insurance company.

NET ASSET VALUE ("NAV") is the value of a single Share of a Portfolio. It is
computed by adding the value of all of a Portfolio's investments and other
assets, subtracting any liabilities and dividing the result by the number of
shares outstanding. The difference between line 1 and line 10 in the Financial
Highlights table represents the change in value of the Share of a Portfolio over
the fiscal period, but not its total return.

RATIO OF NET INVESTMENT INCOME TO AVERAGE NET ASSETS is a Portfolio's net
investment income divided by its average net assets for the stated period.

AVERAGE COMMISSION RATE is the total of a Portfolio's agency commission paid on
equity securities trades divided by the number of shares purchased and sold.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 5
<PAGE>

PERFORMANCE TERMS

This section will help you understand various terms that are commonly used to
describe a Portfolio's performance. You may see references to these terms in our
newsletters or advertisements (or those published by participating insurance
companies) and in media articles. Newsletters and advertisements may include
comparisons of a Portfolio's performance to the performance of other mutual
funds, mutual fund averages or recognized stock market indices. Worldwide Growth
Portfolio and Balanced Portfolio generally measure performance in terms of total
return.

CUMULATIVE TOTAL RETURN represents the actual rate of return on an investment
for a specified period. The Financial Highlights table shows total return for a
single fiscal period. Cumulative total return is generally quoted for more than
one year (e.g., the life of a Portfolio). A cumulative total return does not
show interim fluctuations in the value of an investment.

THE PORTFOLIOS IMPOSE NO SALES OR OTHER CHARGES THAT WOULD AFFECT TOTAL RETURN
COMPUTATIONS. TOTAL RETURN FIGURES INCLUDE THE EFFECT OF DEDUCTING EACH
PORTFOLIO'S EXPENSES, BUT MAY NOT INCLUDE CHARGES AND EXPENSES ATTRIBUTABLE TO
ANY PARTICULAR INSURANCE PRODUCT. PORTFOLIO PERFORMANCE FIGURES ARE BASED UPON
HISTORICAL RESULTS AND ARE NOT INTENDED TO INDICATE FUTURE PERFORMANCE.
INVESTMENT RETURNS AND NET ASSET VALUE WILL FLUCTUATE SO THAT SHARES, WHEN
REDEEMED, MAY BE WORTH MORE OR LESS THAN THEIR ORIGINAL COST.

6 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

THE PORTFOLIOS IN DETAIL

Each Portfolio has an investment objective and policies that are similar to
those of a Janus retail fund, as illustrated in the chart below. Although it is
anticipated that each Portfolio and its corresponding Janus retail fund will
hold similar securities, differences in asset size and cash flow needs as well
as the relative weightings of securities selections may result in differences in
investment performance. Expenses of each Portfolio and its corresponding Janus
retail fund are expected to differ. The variable contract owner will also bear
various insurance-related costs at the insurance company level. You should
review the accompanying separate account prospectus for a summary of contract
fees and expenses.

Policies that are noted as "fundamental" cannot be changed without a shareholder
vote. All other policies, including each Portfolios' investment objective, are
not fundamental and may be changed by the Portfolios' Trustees without a
shareholder vote. You will be notified of any such changes that are material. If
there is a material change in a Portfolio's objective or policies, you should
consider whether that Portfolio remains an appropriate investment for your
variable insurance contract or qualified retirement plan.
EACH OF THE PORTFOLIOS HAS A SIMILAR INVESTMENT
OBJECTIVE AND SIMILAR INVESTMENT POLICIES TO AN EXISTING JANUS RETAIL FUND.

Worldwide Growth Portfolio................................Janus Worldwide Fund
Balanced Portfolio.........................................Janus Balanced Fund

WORLDWIDE GROWTH PORTFOLIO IS DESIGNED FOR LONG-TERM INVESTORS WHO SEEK GROWTH
OF CAPITAL ONLY AND WHO CAN TOLERATE THE GREATER RISKS ASSOCIATED WITH COMMON
STOCK INVESTMENTS.

Investment Objective:..........................................Growth of Capital
Primary Holdings:..................................................Common Stocks
Shareholder's Investment Horizon:......................................Long-Term

TYPES OF INVESTMENTS
Worldwide Growth Portfolio invests primarily in common stocks of foreign and
domestic companies. The Portfolio may at times hold substantial positions in
cash equivalents or interest bearing securities. See "General Portfolio
Policies" on page 9. The Portfolio may invest to a lesser degree in other types
of securities including preferred stocks, warrants, convertible securities and
debt securities when the portfolio manager perceives an opportunity for capital
growth from such securities or to receive a return on idle cash. Some securities
that the Portfolio purchases may be on a when-issued, delayed delivery or
forward commitment basis. The Portfolio may invest up to 25% of its assets in
mortgage- and asset-backed securities, up to 10% of its assets in zero coupon,
pay-in-kind and step coupon securities, and without limit in indexed/structured
securities. The Portfolio will not invest 35% or more of its assets in
high-yield/high-risk securities.

The Portfolio is committed to foreign investing and may invest without limit in
foreign equity and debt securities. The Portfolio may invest directly in foreign
securities denominated in a foreign currency and not publicly traded in the
United States. Other ways of investing in foreign securities include depositary
receipts or shares, and passive foreign investment companies ("PFICs"). The
Portfolio may use futures, options and other derivatives for hedging purposes or
for non-hedging purposes such as seeking to enhance return. See "Additional Risk
Factors" on page 10 for a discussion of the risks associated with foreign
investing and derivatives.

THE FOLLOWING QUESTIONS ARE DESIGNED TO HELP YOU BETTER UNDERSTAND AN INVESTMENT
IN WORLDWIDE GROWTH PORTFOLIO.

Q: HOW ARE COMMON STOCKS SELECTED?

A: Worldwide Growth Portfolio invests substantially all of its assets in
common stocks to the extent its portfolio manager believes that the
relevant market environment favors profitable investing in those securities. The
portfolio manager generally takes a "bottom up" approach to building the
portfolio. In other words, she seeks to identify individual companies with
earnings growth potential that may not be recognized by the market at large.
Although themes may emerge in the Portfolio, securities are generally selected
without regard to any defined industry sector or other similarly defined
selection procedure. Realization of income is not a significant investment
consideration. Any income realized on the Portfolio's investments will be
incidental to its objective.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 7
<PAGE>

Q: ARE THE SAME CRITERIA USED TO SELECT FOREIGN SECURITIES?

A: Generally, yes. The portfolio manager seeks companies that meet her
selection criteria, regardless of country of organization or place of
principal business activity. Foreign securities are generally selected on a
stock-by-stock basis without regard to any defined allocation among countries or
geographic regions. However, certain factors such as expected levels of
inflation, government policies influencing business conditions, the outlook for
currency relationships, and prospects for economic growth among countries,
regions or geographic areas may warrant greater consideration in selecting
foreign securities. See "Additional Risk Factors" on page 10.

Q: WHAT IS THE MAIN RISK OF INVESTING IN WORLDWIDE GROWTH PORTFOLIO?

A: Since the Portfolio usually invests heavily in common stocks, the
fundamental risk is that the value of the stocks the Portfolio holds might
decrease. Stock values may fluctuate in response to the activities of an
individual company or in response to general market and economic conditions.
Historically, common stocks have provided greater long-term returns and have
entailed greater short-term risks than other investment choices. Smaller or
newer issuers are more likely to realize more substantial growth as well as
suffer more significant losses than larger or more established issuers.
Investments in such companies can be both more volatile and more speculative.
See "Additional Risk Factors" on page 10.

Q: WHAT IS MEANT BY "MARKET CAPITALIZATION"?

A: Market capitalization is the most commonly used measure of the size and
value of a company. It is computed by multiplying the current market price
of a share of the company's stock by the total number of its shares outstanding.
Although Worldwide Growth Portfolio does not emphasize companies of any
particular size, a Portfolio with a larger asset base is more likely to invest
in larger, more-established issuers.

Q: HOW DOES WORLDWIDE GROWTH PORTFOLIO TRY TO REDUCE RISK?

A: Diversification of a Portfolio's assets reduces the effect of any single
holding on its overall portfolio value. The Portfolio may also use
futures, options and other derivative instruments to protect its portfolio from
movements in securities' prices and interest rates. The Portfolio may use a
variety of currency hedging techniques, including forward currency contracts, to
manage exchange rate risk when investing directly in foreign markets. See
"Additional Risk Factors" on page 10. In addition, to the extent that the
Portfolio holds a larger cash position, it may not participate in market
declines to the same extent as if the Portfolio remained more fully invested in
common stocks.

BALANCED PORTFOLIO IS DESIGNED FOR INVESTORS WHO PRIMARILY SEEK GROWTH OF
CAPITAL WITH A DEGREE OF EMPHASIS ON INCOME. IT IS NOT DESIGNED FOR INVESTORS
WHO DESIRE A CONSISTENT LEVEL OF INCOME.

BALANCED PORTFOLIO
The investment objective of this Portfolio is long-term capital growth,
consistent with preservation of capital and balanced by current income. It is a
diversified portfolio that, under normal circumstances, pursues its objective by
investing 40-60% of its assets in securities selected primarily for their growth
potential and 40-60% of its assets in securities selected primarily for their
income potential. The Portfolio normally invests at least 25% of its assets in
fixed-income senior securities, which include debt securities and preferred
stocks.

TYPES OF INVESTMENTS
Balanced Portfolio may invest in a combination of common stocks, preferred
stocks, convertible securities, debt securities and other fixed income
securities including corporate bonds and notes, government securities and
indexed/structured securities. Balanced Portfolio may invest in the types of
investments previously described under Worldwide Growth Portfolio on page 7.
Although Balanced Portfolio places some emphasis on the income objective,
investors should keep in mind that the Portfolio is not designed to produce a
consistent level of income.

THE FOLLOWING QUESTIONS ARE DESIGNED TO HELP YOU BETTER UNDERSTAND AN INVESTMENT
IN BALANCED PORTFOLIO.

Q: HOW ARE ASSETS ALLOCATED BETWEEN THE GROWTH AND INCOME COMPONENTS OF
BALANCED PORTFOLIO?

Q: WHAT TYPES OF SECURITIES MAKE UP THE GROWTH COMPONENT OF BALANCED
PORTFOLIO?

A: The growth component of Balanced Portfolio is expected to consist
primarily of common stocks. The selection criteria for common stocks are
described on page 7. Because income is a part of the investment objective of
Balanced Portfolio, the portfolio manager may consider dividend-paying
characteristics to a greater degree in selecting equity securities. Balanced
Portfolio may also find opportunities for capital growth from debt securities
because of anticipated changes in

8 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

interest rates, credit standing, currency relationships or other factors.

Q: WHAT TYPES OF SECURITIES MAKE UP THE INCOME COMPONENT OF BALANCED
PORTFOLIO?

A: The income component of Balanced Portfolio will consist of securities that
the portfolio manager believes have income potential. Such securities may
include equity securities, convertible securities and all types of debt
securities. Equity securities may be included in the income component of
Balanced Portfolio if they currently pay dividends or a portfolio manager
believes they have the potential for either increasing their dividends or
commencing dividends, if none are currently paid.

GENERAL PORTFOLIO POLICIES
In investing their assets, the Portfolios will follow the general policies
listed below. The percentage limitations included in these policies and
elsewhere in this Prospectus apply only at the time of purchase of the security.
For example, if a Portfolio exceeds a limit as a result of market fluctuations
or the sale of other securities, it will not be required to dispose of any
securities.

CASH POSITION
When a Portfolio's manager believes that market conditions are not favorable for
profitable investing or when the portfolio manager is otherwise unable to locate
favorable investment opportunities, a Portfolio's investments may be hedged to a
greater degree and/or its cash or similar investments may increase. In other
words, a Portfolio does not always stay fully invested in stocks and bonds. Cash
or similar investments are a residual - they represent the assets that remain
after the portfolio manager has committed available assets to desirable
investment opportunities. Partly because the portfolio managers act
independently of each other, the cash positions of the Portfolios may vary
significantly. A larger hedged position and/or larger cash position may serve as
a means of preserving capital in unfavorable market conditions.

Securities that a Portfolio may invest in as means of receiving a return on idle
cash include high-grade commercial paper, certificates of deposit, repurchase
agreements or other short-term debt obligations. The Portfolios may also invest
in money market funds (including funds managed by Janus Capital). When a
Portfolio is hedged or its investments in cash or similar investments increase,
it may not participate in stock or bond market advances or declines to the same
extent that it would if a Portfolio was not hedged or remained more fully
invested in stocks or bonds.

DIVERSIFICATION
The Investment Company Act of 1940 (the "1940 Act") classifies investment
companies as either diversified or nondiversified. The Portfolios qualify as
diversified funds under the 1940 Act and are subject to the following
diversification requirements:

- - As a fundamental policy, neither Portfolio may own more than 10% of the
outstanding voting shares of any issuer.

- - As a fundamental policy, with respect to 75% of its total assets, neither
Portfolio will purchase a security of any issuer (other than cash items and
U.S. government securities, as defined in the 1940 Act) if such purchase would
cause a Portfolio's holdings of that issuer to amount to more than 5% of that
Portfolio's total assets.

- - Neither Portfolio will invest more than 25% of its total assets in a single
issuer (other than U.S. government securities).

INTERNAL REVENUE SERVICE (IRS) LIMITATIONS
In addition to the diversification requirements stated above, the Portfolios
intend to comply with the diversification requirements currently imposed by the
IRS on separate accounts of insurance companies as a condition of maintaining
the tax-deferred status of variable contracts. More specific information may be
contained in the participating insurance company's separate account prospectus.

INDUSTRY CONCENTRATION
As a fundamental policy, neither Portfolio will invest 25% or more of its total
assets in any particular industry (excluding U.S. government securities).

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 9
<PAGE>

terms or because of SEC regulations. Janus Capital will follow guidelines
established by the Trustees of the Trust ("Trustees") in making liquidity
determinations for Rule 144A securities and other securities, including
privately placed commercial paper and municipal lease obligations.

BORROWING AND LENDING
Each Portfolio may borrow money and lend securities or other assets, as follows:

- - Each Portfolio may borrow money for temporary or emergency purposes in amounts
up to 25% of its total assets.

- - Each Portfolio may mortgage or pledge securities as collateral for borrowings
in amounts up to 15% of its net assets.

- - As a fundamental policy, each Portfolio may lend securities or other assets
if, as a result, no more than 25% of its total assets would be lent to other
parties.

Under the terms of an exemptive order from the SEC, each Portfolio may borrow
money from or lend money to other funds that permit such transactions and for
which Janus Capital serves as investment adviser. All such borrowing and lending
will be subject to the above percentage limits.

ADDITIONAL RISK FACTORS
FOREIGN SECURITIES
INVESTMENTS IN FOREIGN SECURITIES, INCLUDING THOSE OF FOREIGN GOVERNMENTS, MAY
INVOLVE GREATER RISKS THAN INVESTING IN COMPARABLE DOMESTIC SECURITIES.

Securities of some foreign companies and governments may be traded in the United
States, but many foreign securities are traded primarily in foreign markets. The
risks of foreign investing include:

- - POLITICAL AND ECONOMIC RISK. Foreign investments may be subject to heightened
political and economic risks, particularly in underdeveloped or developing
countries which may have relatively unstable governments and economies based
on only a few industries. In some countries, there is the risk that the
government may take over the assets or operations of a company or that the
government may impose taxes or limits on the removal of a Portfolio's assets
from that country. The Portfolios may invest in emerging market countries.
Emerging market countries involve greater risks such as immature economic
structures, national policies restricting investments by foreigners, and
different legal systems.

- - TRANSACTION COSTS. Transaction costs of buying and selling foreign securities,
including brokerage, tax and custody costs, are generally higher than those
involved in domestic transactions.

INVESTMENTS IN SMALLER COMPANIES
SMALLER OR NEWER COMPANIES MAY SUFFER MORE SIGNIFICANT LOSSES AS WELL AS REALIZE
MORE SUBSTANTIAL GROWTH THAN LARGER OR MORE ESTABLISHED ISSUERS.

FUTURES, OPTIONS AND OTHER DERIVATIVE INSTRUMENTS
Each Portfolio may enter into futures contracts on securities, financial indices
and foreign currencies and options on such contracts ("futures contracts") and
may invest in options on securities, financial indices and foreign currencies
("options"), forward contracts and interest rate swaps and swap-related products
(collectively "derivative instruments"). The Portfolios intend to use most
derivative instruments primarily to hedge against potential adverse movements in
securities prices, foreign currency markets or interest rates. To a limited
extent, the Portfolios may also use derivative instruments for non-hedging
purposes such as seeking to increase its income or otherwise seeking to enhance
return. Please refer to Appendix A to this

10 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

Prospectus and the SAI for a more detailed discussion of these instruments.

The use of derivative instruments exposes the Portfolios to additional
investment risks and transaction costs. Risks inherent in the use of derivative
instruments include:

- - the risk that interest rates, securities prices and currency markets will not
move in the direction that a portfolio manager anticipates;

- - imperfect correlation between the price of derivative instruments and
movements in the prices of the securities, interest rates or currencies being
hedged;

- - the fact that skills needed to use these strategies are different from those
needed to select portfolio securities;

- - inability to close out certain hedged positions to avoid adverse tax
consequences;

Issuers of high-yield/high-risk securities are more vulnerable to real or
perceived economic changes (for instance, an economic downturn or prolonged
period of rising interest rates), political changes or adverse developments
specific to the issuer. Adverse economic, political or other developments may
impair the issuer's ability to service principal and interest obligations, to
meet projected business goals and to obtain additional financing, particularly
if the issuer is highly leveraged. In the event of a default, the Portfolio
would experience a reduction of its income and could expect a decline in the
market value of the defaulted securities.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 11
<PAGE>

supply of and demand for the security. Investment in special situations may
carry an additional risk of loss in the event that the anticipated development
does not occur or does not attract the expected attention.

See Appendix A for risks associated with certain other investments.

12 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

MANAGEMENT OF THE PORTFOLIO

TRUSTEES

INVESTMENT ADVISER
Janus Capital, 100 Fillmore Street, Denver, Colorado 80206-4928, is the
investment adviser to the Portfolios and is responsible for the day-to-day
management of the investment portfolios and other business affairs of the
Portfolios.

Janus Capital furnishes continuous advice and recommendations concerning the
Portfolio's investments. Janus Capital also furnishes certain administrative,
compliance and accounting services for the Portfolios, and may be reimbursed by
the Portfolios for its costs in providing those services. In addition, Janus
Capital employees serve as officers of the Trust and Janus Capital provides
office space for the Portfolios and pays the salaries, fees and expenses of all
Portfolio officers and those Trustees who are affiliated with Janus Capital.

INVESTMENT PERSONNEL
PORTFOLIO MANAGERS
HELEN YOUNG HAYES is Executive Vice President and portfolio manager of Worldwide
Growth Portfolio and co-manager of International Growth Portfolio, which she has
managed or co-managed since inception. Ms. Hayes joined Janus Capital in 1987
and has managed or co-managed Janus Worldwide Fund and Janus Overseas Fund since
their inceptions. She holds a Bachelor of Arts in Economics from Yale University
and is a Chartered Financial Analyst.

BLAINE P. ROLLINS is Executive Vice President and portfolio manager of Balanced
Portfolio, which he has managed since May 1996. Mr. Rollins has managed the
Equity Income Portfolio since inception. He is an assistant portfolio manager of
Growth Portfolio. Mr. Rollins joined Janus Capital in 1990 and has managed Janus
Balanced Fund since January 1996 and Janus Equity Income Fund since June 1996.
He has been an assistant portfolio manager of Janus Fund since January 1995. He
gained experience as a fixed-income trader and equity research analyst prior to
managing Balanced Portfolio. He holds a Bachelor of Science in Finance from the
University of Colorado and is a Chartered Financial Analyst.

ASSISTANT PORTFOLIO MANAGER
LAURENCE J. CHANG is assistant portfolio manager of Worldwide Growth Portfolio,
and co-manager of International Growth Portfolio. Mr. Chang also co-manages
Janus Overseas Fund and is assistant portfolio manager of Janus Worldwide Fund.
He received an undergraduate degree with honors in religion and philosophy from
Dartmouth College and a Master's Degree in Political Science from Stanford
University. He is a Chartered Financial Analyst.

PERSONAL INVESTING
Janus Capital does not permit portfolio managers to purchase and sell securities
for their own accounts, except under the limited exceptions contained in Janus
Capital's policy governing personal investing. Janus Capital's policy requires
investment and other personnel to conduct their personal investment activities
in a manner that Janus Capital believes is not detrimental to the Portfolio or
Janus Capital's other advisory clients. See the SAI for more detailed
information.

MANAGEMENT EXPENSES
Each Portfolio pays Janus Capital a management fee which is calculated daily.
The advisory agreement with each Portfolio spells out the management fee and
other expenses that the Portfolios must pay. Each of the Portfolios is subject
to the following management fee schedule (expressed as an annual rate):

<TABLE>
<CAPTION>
AVERAGE DAILY
NET ASSETS ANNUAL RATE
FEE SCHEDULE OF PORTFOLIO PERCENTAGE(%)
- --------------------------------------------------------------
<S> <C> <C>
Worldwide Growth and First $300 Million 0.75
Balanced Portfolios Next $200 Million 0.70
Over $500 Million 0.65
- --------------------------------------------------------------
</TABLE>

Janus Capital has agreed to reduce each Portfolio's advisory fee to the extent
that such fee exceeds the effective rate of the corresponding Janus retail
fund. Janus Capital may terminate this fee reduction at any time upon at least
90 days' notice to the Trustees. The effective rate is the advisory fee
calculated by the corresponding retail fund as of the last day of each
calendar quarter (expressed as an annual rate). The effective rate of Janus
Worldwide Fund and Janus Balanced Fund was .65% and .73%, respectively, for
the quarter ended March 31, 1998.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 13
<PAGE>

Differences in the actual management fees incurred by the Portfolios are due
primarily to variances in the asset sizes of the corresponding retail funds. As
asset size increases, the annual rate of the management fee declines in
accordance with the above schedule. In addition, the Shares of each Portfolio
incur expenses not assumed by Janus Capital, including transfer agent and
custodian fees and expenses, legal and auditing fees, printing and mailing costs
of sending reports and other information to existing shareholders, and
independent Trustees' fees and expenses. The fee schedule for the Worldwide
Growth and Balanced Portfolios was effective July 1, 1997.

During the most recent fiscal year the Portfolios paid the following management
fees expressed as a percentage of net assets: Worldwide Growth Portfolio .66%
and Balanced Portfolio .76%.

PORTFOLIO TRANSACTIONS
Purchases and sales of securities on behalf of the Portfolios are executed by
broker-dealers selected by Janus Capital. Broker-dealers are selected on the
basis of their ability to obtain best price and execution for a Portfolio's
transactions and recognizing brokerage, research and other services provided to
the Portfolios and to Janus Capital. Janus Capital may consider sales of shares
of the Portfolios or other Janus funds by a broker-dealer or the recommendation
of a broker-dealer to its customers that they purchase Portfolio shares as a
factor in the selection of broker-dealers to execute portfolio transactions.
Janus Capital may also consider payments made by brokers effecting transactions
for the Portfolio i) to the Portfolio or ii) to other persons on behalf of the
Portfolio for services provided to the Portfolio for which it would be obligated
to pay. The Portfolios' Trustees have authorized Janus Capital to place
portfolio transactions on an agency basis with a broker-dealer affiliated with
Janus Capital. When transactions for a Portfolio are effected with that
broker-dealer, the commissions payable by the Portfolio are credited against
certain Portfolio operating expenses serving to reduce those expenses. The SAI
further explains the selection of broker-dealers.

OTHER SERVICE PROVIDERS
The following parties provide the Portfolios with administrative and other
services.

CUSTODIAN
State Street Bank and Trust Company
P.O. Box 0351
Boston, Massachusetts 02117-0351

TRANSFER AGENT
Janus Service Corporation
P.O. Box 173375
Denver, Colorado 80217

Janus Service Corporation is a wholly-owned subsidiary of Janus Capital.

14 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

accounts or plans to withdraw its investment in one or more Portfolios or
substitute shares of another Portfolio. If this occurs, a Portfolio may be
forced to sell securities at disadvantageous prices. In addition, the Trustees
may refuse to sell shares of any Portfolio to any separate account or may
suspend or terminate the offering of a Portfolio's shares if such action is
required by law or regulatory authority or is in the best interests of that
Portfolio's shareholders. It is possible that a qualified plan investing in the
Retirement Shares of the Portfolios could lose its qualified plan status under
the Internal Revenue Code, which could have adverse tax consequences on
insurance company separate accounts investing in the Shares. Janus Capital
intends to monitor such qualified plans and the Portfolios may discontinue sales
to a qualified plan and require plan participants with existing investments in
the Retirement Shares to redeem those investments if a plan loses (or in the
opinion of Janus Capital is at risk of losing) its qualified plan status.

MASTER/FEEDER OPTION
The Trust may in the future seek to achieve any Portfolio's investment objective
by investing all of that Portfolio's assets in another investment company having
the same investment objective and substantially the same investment policies and
restrictions as those applicable to that Portfolio. Unless otherwise required by
law, this policy may be implemented by the Trustees without shareholder
approval.

THE VALUATION OF SHARES
The NAV of the Shares of a Portfolio is determined at the close of the regular
trading session of the New York Stock Exchange (the "NYSE") (normally 4:00 p.m.,
New York time) each day that the NYSE is open. NAV per Share is determined by
dividing the total value of the securities and other assets, less liabilities,
by the total number of Shares outstanding.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 15
<PAGE>

DISTRIBUTIONS AND TAXES

DISTRIBUTIONS
TO AVOID TAXATION OF THE PORTFOLIOS, THE INTERNAL REVENUE CODE REQUIRES EACH
PORTFOLIO TO DISTRIBUTE NET INCOME AND ANY NET GAINS REALIZED BY ITS INVESTMENTS
ANNUALLY. ORDINARY INCOME FROM DIVIDENDS AND INTEREST AND ANY NET REALIZED
SHORT-TERM GAINS ARE PAID TO SHAREHOLDERS AS ORDINARY INCOME DIVIDENDS. NET
REALIZED LONG-TERM GAINS, IF ANY, ARE PAID TO SHAREHOLDERS AS CAPITAL GAINS
DISTRIBUTIONS. EACH CLASS OF EACH PORTFOLIO MAKES SEMIANNUAL DISTRIBUTIONS IN
JUNE AND DECEMBER OF SUBSTANTIALLY ALL OF ITS INVESTMENT INCOME AND AN ANNUAL
DISTRIBUTION IN JUNE OF ITS NET REALIZED GAINS, IF ANY. ALL DIVIDENDS AND
CAPITAL GAINS DISTRIBUTIONS FROM SHARES OF A PORTFOLIO WILL BE AUTOMATICALLY
REINVESTED INTO ADDITIONAL SHARES OF THAT PORTFOLIO.

HOW DISTRIBUTIONS AFFECT NAV
Distributions are paid to shareholders as of the record date of the distribution
of a Portfolio, regardless of how long the shares have been held. Undistributed
income and realized gains are included in the daily NAV of a Portfolio's Shares.
The Share price of the Portfolio drops by the amount of the distribution, net of
any subsequent market fluctuations. For example, assume that on December 31, the
Shares of Worldwide Growth Portfolio declared a dividend in the amount of $0.25
per share. If the price of Worldwide Growth Portfolio's Shares was $10.00 on
December 30, the Share price on December 31 would be $9.75, barring market
fluctuations.

The Portfolios do not expect to pay any federal income or excise taxes because
it intends to meet certain requirements of the Internal Revenue Code. In
addition, each Portfolio intends to qualify under the Internal Revenue Code with
respect to the diversification requirements related to the tax-deferred status
of insurance company separate accounts.

16 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

SHAREHOLDER'S GUIDE

INVESTORS MAY NOT PURCHASE OR REDEEM SHARES OF THE PORTFOLIOS DIRECTLY. SHARES
MAY BE PURCHASED OR REDEEMED ONLY THROUGH VARIABLE INSURANCE CONTRACTS OFFERED
BY THE SEPARATE ACCOUNTS OF PARTICIPATING INSURANCE COMPANIES OR THROUGH
QUALIFIED RETIREMENT PLANS. REFER TO THE PROSPECTUS FOR THE PARTICIPATING
INSURANCE COMPANY'S SEPARATE ACCOUNT OR YOUR PLAN DOCUMENTS FOR INSTRUCTIONS ON
PURCHASING OR SELLING OF VARIABLE INSURANCE CONTRACTS AND ON HOW TO SELECT
PORTFOLIOS AS AN INVESTMENT OPTION FOR A CONTRACT OR A QUALIFIED PLAN.

PURCHASES
Purchases of Shares may be made only by the separate accounts of insurance
companies for the purpose of funding variable insurance contracts or by
qualified plans. Refer to the prospectus of the appropriate insurance company's
separate account or your plan documents for information on how to invest in the
Shares of each Portfolio.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 17
<PAGE>

APPENDIX A

GLOSSARY OF INVESTMENT TERMS
This glossary provides a more detailed description of some of the types of
securities and other instruments in which the Portfolios may invest. The
Portfolios may invest in these instruments to the extent permitted by its
investment objective and policies. The Portfolios are not limited by this
discussion and may invest in any other types of instruments not precluded by the
policies discussed elsewhere in this Prospectus. Please refer to the SAI for a
more detailed discussion of certain instruments.

CONVERTIBLE SECURITIES are preferred stocks or bonds that pay a fixed dividend
or interest payment and are convertible into common stock at a specified price
or conversion ratio.

HIGH-YIELD/HIGH-RISK SECURITIES are securities that are rated below investment
grade by the primary rating agencies (BB or lower by Standard & Poor's and Ba or
lower by Moody's). Other terms commonly used to describe such securities include
"lower rated bonds," "noninvestment grade bonds" and "junk bonds."

MORTGAGE- AND ASSET-BACKED SECURITIES are shares in a pool of mortgages or other
debt. These securities are generally pass-through securities, which means that
principal and interest payments on the underlying securities (less servicing
fees) are passed through to shareholders on a pro rata basis. These securities
involve prepayment risk, which is the risk that the underlying mortgages or
other debt may be refinanced or paid off prior to their maturities during
periods of declining interest rates. In that case, the portfolio manager may
have to reinvest the proceeds from the securities at a lower rate. Potential
market gains on a security subject to prepayment risk may be more limited than
potential market gains on a comparable security that is not subject to
prepayment risk.

18 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

RULE 144A SECURITIES are securities that are not registered for sale to the
general public under the Securities Act of 1933, but that may be resold to
certain institutional investors.

STANDBY COMMITMENTS are obligations purchased by a Portfolio from a dealer that
give the Portfolio the option to sell a security to the dealer at a specified
price.

WHEN-ISSUED, DELAYED DELIVERY AND FORWARD TRANSACTIONS generally involve the
purchase of a security with payment and delivery at some time in the future -
i.e., beyond normal settlement. The Portfolios do not earn interest on such
securities until settlement and bears the risk of market value fluctuations
between the purchase and settlement dates. New issues of stocks and bonds,
private placements and U.S. government securities may be sold in this manner.

II. FUTURES, OPTIONS
AND OTHER DERIVATIVES
FORWARD CONTRACTS are contracts to purchase or sell a specified amount of a
financial instrument for an agreed upon price at a specified time. Forward
contracts are not currently exchange traded and are typically negotiated on an
individual basis. The Portfolios may enter into forward currency contracts to
hedge against declines in the value of non-dollar denominated securities or to
reduce the impact of currency appreciation on purchases of non-dollar
denominated securities. The Portfolios may also enter into forward contracts to
purchase or sell securities or other financial indices.

INDEXED/STRUCTURED SECURITIES are typically short- to intermediate-term debt
securities whose value at maturity or interest rate is linked to currencies,
interest rates, equity securities, indices, commodity prices or other financial
indicators. Such securities may be positively or negatively indexed (i.e., their
value may increase or decrease if the reference index or instrument
appreciates). Indexed/structured securities may have return characteristics
similar to direct investments in the underlying instruments and may be more
volatile than the under-lying instruments. A Portfolio bears the market risk of
an investment in the underlying instruments, as well as the credit risk of the
issuer.

INTEREST RATE SWAPS involve the exchange by two parties of their respective
commitments to pay or receive interest (e.g., an exchange of floating rate
payments for fixed rate payments).

INVERSE FLOATERS are debt instruments whose interest rate bears an inverse
relationship to the interest rate on another

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 19
<PAGE>

20 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>
JANUS ASPEN SERIES
PROSPECTUS
Worldwide Growth Portfolio
Balanced Portfolio

[JANUS LOGO]

P.O. Box 173375 o Denver, CO 80217-3375 o 1-800-525-1068
(5/98)
<PAGE>

JANUS ASPEN SERIES

Prospectus

MAY 1, 1998

THESE SECURITIES HAVE NOT BEEN APPROVED BY THE SEC NOR HAS THE SEC PASSED ON THE
ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A
CRIMINAL OFFENSE.

THIS PROSPECTUS DOES NOT CONSTITUTE AN OFFER TO SELL SECURITIES IN ANY STATE OR
OTHER JURISDICTION TO ANY PERSON TO WHOM IT IS UNLAWFUL TO MAKE SUCH AN OFFER IN
SUCH STATE OR OTHER JURISDICTION.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

CONTENTS

<TABLE>
<S> <C>
THE PORTFOLIOS AT A GLANCE
Brief description of the Portfolios......................... 2
EXPENSE INFORMATION
Each Portfolio's annual operating expenses.................. 3
Financial Highlights - a summary of financial data.......... 4
PERFORMANCE TERMS
An explanation of performance terms......................... 7
THE PORTFOLIOS IN DETAIL
Investment Objectives and Policies.......................... 8
General Portfolio Policies.................................. 9
Additional Risk Factors..................................... 10
MANAGEMENT OF THE PORTFOLIO
Investment Adviser and Investment Personnel................. 13
Personal Investing.......................................... 13
Management Expenses......................................... 13
Portfolio Transactions...................................... 14
Other Service Providers..................................... 14
Other Information........................................... 14
DISTRIBUTIONS AND TAXES
Distributions............................................... 16
Taxes....................................................... 16
SHAREHOLDER'S GUIDE
Purchases................................................... 17
Redemptions................................................. 17
Shareholder Communications.................................. 17
APPENDIX A
Glossary of Investment Terms................................ 18
</TABLE>

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 1
<PAGE>

PORTFOLIOS AT A GLANCE

2 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

EXPENSE INFORMATION

SHAREHOLDER TRANSACTION EXPENSE (APPLICABLE TO EACH PORTFOLIO)

ANNUAL OPERATING EXPENSES (after fee reductions)(1)
(expressed as a percentage of average net assets)

<TABLE>
<CAPTION>
- ---------------------------------------------------------------------------------------------------------------
MANAGEMENT OTHER TOTAL OPERATING
FEE EXPENSES EXPENSES
- ---------------------------------------------------------------------------------------------------------------
<S> <C> <C> <C>
Growth Portfolio 0.65% 0.05% 0.70%
Worldwide Growth Portfolio 0.66% 0.08% 0.74%
- ---------------------------------------------------------------------------------------------------------------
</TABLE>

(1) Management fees for Growth and Worldwide Growth Portfolios reflect a reduced
fee schedule effective July 1, 1997. The management fee for each of these
Portfolios reflects the new rate applied to net assets as of December 31,
1997. Other expenses are based on the gross expenses of the Shares before
expense offset arrangements for the fiscal year ended December 31, 1997. The
information for each Portfolio is net of fee reductions from Janus Capital.
Fee reductions for Growth and Worldwide Growth Portfolios reduce the
management fee to the level of the corresponding Janus retail fund. Without
such reductions, the Management Fee, Other Expenses and Total Operating
Expenses for the Shares would have been 0.74%, 0.04%, and 0.78% for Growth
Portfolio and 0.72%, 0.09% and 0.81% for Worldwide Growth Portfolio. Janus
Capital may modify or terminate the reductions at any time upon at least 90
days' notice to the Trustees.

EXAMPLE
Assume you invest $1,000, the Shares of the Portfolios return 5% annually and
each Portfolio's expense ratio remains as listed above. The example below shows
the operating expenses that you would indirectly bear as an investor in the
Shares of the Portfolios.

<TABLE>
<CAPTION>
- ---------------------------------------------------------------------------------------------------------------
1 YEAR 3 YEARS 5 YEARS 10 YEARS
- ---------------------------------------------------------------------------------------------------------------
<S> <C> <C> <C> <C>
Growth Portfolio $7 $22 $39 $87
Worldwide Growth Portfolio $8 $24 $41 $92
- ---------------------------------------------------------------------------------------------------------------
</TABLE>

THE EXAMPLE SHOULD NOT BE CONSIDERED A REPRESENTATION OF PAST OR FUTURE RETURNS
OR EXPENSES WHICH MAY BE MORE OR LESS THAN THOSE SHOWN.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 3
<PAGE>

FINANCIAL HIGHLIGHTS

<TABLE>
<CAPTION>
GROWTH PORTFOLIO
INSTITUTIONAL SHARES 1997 1996 1995 1994 1993(1)
- -----------------------------------------------------------------------------------------------------------------------------
<C> <S> <C> <C> <C> <C> <C>
1. Net asset value, beginning of period $15.51 $13.45 $10.57 $10.32 $10.00
- -----------------------------------------------------------------------------------------------------------------------------
INCOME FROM INVESTMENT OPERATIONS:
2. Net investment income .15 .17 .28 .09 .03
3. Net gains or (losses) on securities (both
realized and unrealized) 3.34 2.29 2.90 .20 .32
- -----------------------------------------------------------------------------------------------------------------------------
4. Total from investment operations 3.49 2.46 3.18 .29 .35
- -----------------------------------------------------------------------------------------------------------------------------
LESS DISTRIBUTIONS:
5. Dividends (from net investment income) (.15) (.17) (.30) (.04) (.03)
6. Tax return of capital distributions -- -- -- -- --
7. Distributions (from capital gains) (.37) (.23) -- -- --
- -----------------------------------------------------------------------------------------------------------------------------
8. Total distributions (.52) (.40) (.30) (.04) (.03)
- -----------------------------------------------------------------------------------------------------------------------------
9. Net asset value, end of period $18.48 $15.51 $13.45 $10.57 $10.32
- -----------------------------------------------------------------------------------------------------------------------------
10. Total return* 22.75% 18.45% 30.17% 2.76% 3.50%
- -----------------------------------------------------------------------------------------------------------------------------
11. Net assets, end of period (in thousands) $608,281 $325,789 $126,911 $43,549 $7,482
12. Average net assets for the period (in thousands) $477,914 $216,125 $77,344 $26,464 $3,191
13. Ratio of gross expenses to average net assets** 0.70%(7) 0.69%(6) 0.78%(5) N/A N/A
14. Ratio of net expenses to average net assets** 0.69% 0.69% 0.76% 0.88%(2)(4) 0.25%(3)
15. Ratio of net investment income to average net
assets** 0.91% 1.39% 1.24% 1.45% 2.54%
16. Portfolio turnover rate** 122% 87% 185% 169% 162%
17. Average commission rate $0.0500 $0.0466 N/A N/A N/A
- -----------------------------------------------------------------------------------------------------------------------------
</TABLE>

4 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

<TABLE>
<CAPTION>
WORLDWIDE GROWTH PORTFOLIO
INSTITUTIONAL SHARES 1997 1996 1995 1994 1993(1)
- -----------------------------------------------------------------------------------------------------------------------------
<C> <S> <C> <C> <C> <C> <C>
1. Net asset value, beginning of period $19.44 $15.31 $12.07 $11.89 $10.00
- -----------------------------------------------------------------------------------------------------------------------------
INCOME FROM INVESTMENT OPERATIONS:
2. Net investment income .16 .16 .11 .04 .02
3. Net gains or (losses) on securities (both
realized and unrealized) 4.14 4.27 3.19 .14 1.89
- -----------------------------------------------------------------------------------------------------------------------------
4. Total from investment operations 4.30 4.43 3.30 .18 1.91
- -----------------------------------------------------------------------------------------------------------------------------
LESS DISTRIBUTIONS:
5. Dividends (from net investment income) (.17) (.17) (.06) -- (.01)
6. Dividends (in excess of net investment income) (.02) -- -- -- --
7. Tax return of capital distributions -- -- -- -- --
8. Distributions (from capital gains) (.16) (.13) -- -- (.01)
- -----------------------------------------------------------------------------------------------------------------------------
9. Total distributions (.35) (.30) (.06) -- (.02)
- -----------------------------------------------------------------------------------------------------------------------------
10. Net asset value, end of period $23.39 $19.44 $15.31 $12.07 $11.89
- -----------------------------------------------------------------------------------------------------------------------------
11. Total return* 22.15% 29.04% 27.37% 1.53% 19.10%
- -----------------------------------------------------------------------------------------------------------------------------
12. Net assets, end of period (in thousands) $1,576,548 $582,603 $108,563 $37,728 $4,856
13. Average net assets for the period (in thousands) $1,148,951 $304,111 $59,440 $22,896 $2,200
14. Ratio of gross expenses to average net assets** 0.74%(7) 0.80%(6) 0.90%(5) N/A N/A
15. Ratio of net expenses to average net assets** 0.74% 0.80% 0.87% 1.18%(2)(4) 0.25%(3)
16. Ratio of net investment income to average net
assets** 0.67% 0.83% 0.95% 0.50% 0.84%
17. Portfolio turnover rate** 80% 62% 113% 217% 57%
18. Average commission rate $0.0337 $0.0345 N/A N/A N/A
- -----------------------------------------------------------------------------------------------------------------------------
</TABLE>

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 5
<PAGE>

UNDERSTANDING THE
FINANCIAL HIGHLIGHTS

This section is designed to help you better understand the information
summarized in the Financial Highlights table. The table contains important
historical operating information that may be useful in making your investment
decision or understanding how your investment has performed. The Portfolios'
Annual Report contains additional information about each Portfolio's
performance, including a comparison to an appropriate securities index. To
request a copy of the Annual Report, please call or write your insurance
company.

NET ASSET VALUE ("NAV") is the value of a single Share of a Portfolio. It is
computed by adding the value of all of a Portfolio's investments and other
assets, subtracting any liabilities and dividing the result by the number of
shares outstanding. The difference between NET ASSET VALUE, BEGINNING OF PERIOD
and NET ASSET VALUE, END OF PERIOD in the Financial Highlights table represents
the change in value of a Share of a Portfolio over the fiscal period, but not
its total return.

RATIO OF NET INVESTMENT INCOME TO AVERAGE NET ASSETS is a Portfolio's net
investment income divided by its average net assets for the stated period.

AVERAGE COMMISSION RATE is the total of a Portfolio's agency commission paid on
equity securities trades divided by the number of shares purchased and sold.

6 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

PERFORMANCE TERMS

This section will help you understand various terms that are commonly used to
describe a Portfolio's performance. You may see references to these terms in our
newsletters or advertisements (or those published by participating insurance
companies) and in media articles. Newsletters and advertisements may include
comparisons of a Portfolio's performance to the performance of other mutual
funds, mutual fund averages or recognized stock market indices. Growth Portfolio
and Worldwide Growth Portfolio generally measure performance in terms of total
return.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 7
<PAGE>

THE PORTFOLIOS IN DETAIL

Each Portfolio has an investment objective and policies that are similar to
those of a Janus retail fund, as illustrated in the chart below. Although it is
anticipated that each Portfolio and its corresponding retail fund will hold
similar securities, differences in asset size and cash flow needs as well as the
relative weightings of securities selections may result in differences in
investment performance. Expenses of each Portfolio and its corresponding retail
fund are expected to differ. The variable contract owner will also bear various
insurance-related costs at the insurance company level. You should review the
accompanying separate account prospectus for a summary of contract fees and
expenses.

EACH OF THE PORTFOLIOS HAS A SIMILAR INVESTMENT
OBJECTIVE AND SIMILAR INVESTMENT POLICIES TO AN EXISTING JANUS RETAIL FUND.

Growth Portfolio....................................................Janus Fund
Worldwide Growth Portfolio................................Janus Worldwide Fund

GROWTH PORTFOLIO AND WORLDWIDE GROWTH PORTFOLIO ARE DESIGNED FOR LONG-TERM
INVESTORS WHO SEEK GROWTH OF CAPITAL ONLY AND WHO CAN TOLERATE THE GREATER RISKS
ASSOCIATED WITH COMMON STOCK INVESTMENTS.

WORLDWIDE GROWTH PORTFOLIO
The investment objective of this Portfolio is long-term growth of capital in a
manner consistent with the preservation of capital. It is a diversified
Portfolio that pursues its investment objective primarily through investments in
common stocks of foreign and domestic issuers. The Portfolio has the flexibility
to invest on a worldwide basis in companies and other organizations of any size,
regardless of country of organization or place of principal business activity.
The Portfolio normally invests in issuers from at least five different
countries, including the United States. The Portfolio may at times invest in
fewer than five countries or even a single country.

TYPES OF INVESTMENTS
Each Portfolio invests primarily in common stocks of foreign and domestic
companies. However, the percentage of each Portfolio's assets invested in common
stocks will vary and each Portfolio may at times hold substantial positions in
cash equivalents or interest bearing securities. See "General Portfolio
Policies" on page 9. Each Portfolio may invest to a lesser degree in other types
of securities including preferred stocks, warrants, convertible securities and
debt securities when its portfolio manager perceives an opportunity for capital
growth from such securities or to receive a return on idle cash. Some securities
that the Portfolios purchase may be on a when-issued, delayed delivery or
forward commitment basis. The Portfolios may invest up to 25% of their assets in
mortgage- and asset-backed securities, up to 10% of their assets in zero coupon,
pay-in-kind and step coupon securities, and without limit in indexed/structured
securities. Neither Portfolio will invest 35% or more of its assets in
high-yield/high-risk securities.

Although Worldwide Growth Portfolio is committed to foreign investing, Growth
Portfolio may also invest without limit in foreign equity and debt securities.
The Portfolios may invest directly in foreign securities denominated in a
foreign currency and not publicly traded in the United States. Other ways of
investing in foreign securities include depositary receipts or shares, and
passive foreign investment companies ("PFICs"). These Portfolios may use
futures, options and other derivatives for hedging purposes or for non-hedging
purposes such as seeking to enhance return. See "Additional Risk Factors" on
page 10 for a discussion of the risks associated with foreign investing and
derivatives.

8 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

THE FOLLOWING QUESTIONS ARE DESIGNED TO HELP YOU BETTER UNDERSTAND AN INVESTMENT
IN GROWTH PORTFOLIO OR WORLDWIDE GROWTH PORTFOLIO.

Q: HOW ARE COMMON STOCKS SELECTED?

A: Each Portfolio invests substantially all of its assets in common stocks to
the extent its portfolio manager believes that the relevant market
environment favors profitable investing in those securities. Portfolio managers
generally take a "bottom up" approach to building their portfolios. In other
words, they seek to identify individual companies with earnings growth potential
that may not be recognized by the market at large. Although themes may emerge in
a Portfolio, securities are generally selected without regard to any defined
industry sector or other similarly defined selection procedure. Realization of
income is not a significant investment consideration. Any income realized on
these Portfolio's investments will be incidental to their objectives.

Q: ARE THE SAME CRITERIA USED TO SELECT FOREIGN SECURITIES?

Q: WHAT IS THE MAIN RISK OF INVESTING IN THE PORTFOLIOS?

A: Since the Portfolios usually invest heavily in common stocks, the
fundamental risk is that the value of the stocks a Portfolio holds might
decrease. Stock values may fluctuate in response to the activities of an
individual company or in response to general market and economic conditions.
Historically, common stocks have provided greater long-term returns and have
entailed greater short-term risks than other investment choices. Smaller or
newer issuers are more likely to realize more substantial growth as well as
suffer more significant losses than larger or more established issuers.
Investments in such companies can be both more volatile and more speculative.
See "Additional Risk Factors" on page 10.

Q: HOW DO THE PORTFOLIOS TRY TO REDUCE RISK?

A: Diversification of a Portfolio's assets reduces the effect of any single
holding on its overall portfolio value. A Portfolio may use futures,
options and other derivative instruments to protect its portfolio from movements
in securities' prices and interest rates. The Portfolios may also use a variety
of currency hedging techniques, including forward currency contracts, to manage
exchange rate risk when investing directly in foreign markets. See "Additional
Risk Factors" on page 10. In addition, to the extent that a Portfolio holds a
larger cash position, it may not participate in market declines to the same
extent as if it remained more fully invested in common stocks.

CASH POSITION
When a Portfolio's manager believes that market conditions are not favorable for
profitable investing or when the portfolio manager is otherwise unable to locate
favorable investment opportunities, a Portfolio's investments may be hedged to a
greater degree and/or its cash or similar investments may increase. In other
words, the Portfolios do not always stay fully invested in stocks and bonds.
Cash or similar investments are a residual - they represent the assets that
remain after a portfolio manager has committed available assets to desirable
investment opportunities. Partly because the portfolio managers act
independently of each other, the cash positions of the Portfolios may vary
significantly. A larger hedged position and/or larger cash position may serve as
a means of preserving capital in unfavorable market conditions.

- - As a fundamental policy, neither Portfolio may own more than 10% of the
outstanding voting shares of any issuer.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 9
<PAGE>

- - a Portfolio's holdings of that issuer to amount to more than 5% of that
Portfolio's total assets.

- - Neither Portfolio will invest more than 25% of its total assets in a single
issuer (other than U.S. government securities).

INDUSTRY CONCENTRATION
As a fundamental policy, neither Portfolio will invest 25% or more of its total
assets in any particular industry (excluding U.S. government securities).

ILLIQUID INVESTMENTS
Each Portfolio may invest up to 15% of its net assets in illiquid investments,
including restricted securities or private placements that are not deemed to be
liquid by Janus Capital. If illiquid securities exceed 15% of a Portfolio's net
assets after the time of purchase, the Portfolio will take steps to reduce in an
orderly fashion its holdings of illiquid securities. An illiquid investment is a
security or other position that cannot be disposed of quickly in the normal
course of business. Some securities cannot be sold to the U.S. public because of
their terms or because of SEC regulations. Janus Capital will follow guidelines
established by the Trustees of the Trust ("Trustees") in making liquidity
determinations for Rule 144A securities and other securities, including
privately placed commercial paper and municipal lease obligations.

BORROWING AND LENDING
Each Portfolio may borrow money and lend securities or other assets, as follows:

- - Each Portfolio may borrow money for temporary or emergency purposes in amounts
up to 25% of its total assets.

- - Each Portfolio may mortgage or pledge securities as collateral for borrowings
in amounts up to 15% of its net assets.

- - As a fundamental policy, each Portfolio may lend securities or other assets
if, as a result, no more than 25% of its total assets would be lent to other
parties.

Under the terms of an exemptive order received from the SEC, each Portfolio may
borrow money from or lend money to other funds that permit such transactions and
for which Janus Capital serves as investment adviser. All such borrowing and
lending will be subject to the above percentage limits.

ADDITIONAL RISK FACTORS

FOREIGN SECURITIES
INVESTMENTS IN FOREIGN SECURITIES, INCLUDING THOSE OF FOREIGN GOVERNMENTS, MAY
INVOLVE GREATER RISKS THAN INVESTING IN COMPARABLE DOMESTIC SECURITIES.

Securities of some foreign companies and governments may be traded in the United
States, but many foreign securities are traded primarily in foreign markets. The
risks of foreign investing include:

- - POLITICAL AND ECONOMIC RISK. Foreign investments may be subject to heightened
political and economic risks, particularly in underdeveloped or developing
countries which may have relatively unstable governments and economies based
on only a few industries. In some countries, there is the risk that the
government may take over the assets or operations of a company or that the
government may impose taxes or limits on the removal of a Portfolio's assets
from that country. The Portfolios may invest in emerging market countries.
Emerging market countries involve greater risks such as immature economic
structures, national policies restricting investments by foreigners, and
different legal systems.

- - MARKET RISK. Foreign securities markets, particularly those of underdeveloped
or developing countries, may be less liquid

10 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

and more volatile than domestic markets. Certain markets may require payment
for securities before delivery and delays may be encountered in settling
securities transactions. In some foreign markets, there may not be protection
against failure by other parties to complete transactions. There may be
limited legal recourse against an issuer in the event of a default on a debt
instrument.

- - TRANSACTION COSTS. Transaction costs of buying and selling foreign securities,
including brokerage, tax and custody costs, are generally higher than those
involved in domestic transactions.

INVESTMENTS IN SMALLER COMPANIES
SMALLER OR NEWER COMPANIES MAY SUFFER MORE SIGNIFICANT LOSSES AS WELL AS REALIZE
MORE SUBSTANTIAL GROWTH THAN LARGER OR MORE ESTABLISHED ISSUERS.

FUTURES, OPTIONS AND OTHER DERIVATIVE INSTRUMENTS
Each Portfolio may enter into futures contracts on securities, financial indices
and foreign currencies and options on such contracts ("futures contracts") and
may invest in options on securities, financial indices and foreign currencies
("options"), forward contracts and interest rate swaps and swap-related products
(collectively "derivative instruments"). The Portfolios intend to use most
derivative instruments primarily to hedge against potential adverse movements in
securities prices, foreign currency markets or interest rates. To a limited
extent, the Portfolios may also use derivative instruments for non-hedging
purposes such as seeking to increase a Portfolio's income or otherwise seeking
to enhance return. Please refer to Appendix A to this Prospectus and the SAI for
a more detailed discussion of these instruments.

The use of derivative instruments exposes the Portfolios to additional
investment risks and transaction costs. Risks inherent in the use of derivative
instruments include:

- - the risk that interest rates, securities prices and currency markets will not
move in the direction that a portfolio manager anticipates;

- - imperfect correlation between the price of derivative instruments and
movements in the prices of the securities, interest rates or currencies being
hedged;

- - the fact that skills needed to use these strategies are different from those
needed to select portfolio securities;

- - inability to close out certain hedged positions to avoid adverse tax
consequences;

meet projected business goals and to obtain additional financing, particularly
if the issuer is highly leveraged. In the event of a default, a Portfolio would
experience a reduction of its income and could expect a decline in the market
value of the defaulted securities.

The market prices of high-yield/high-risk securities structured as zero coupon
or pay-in-kind securities are generally affected to a greater extent by interest
rate changes and tend to be more volatile than securities which pay interest
periodically. In addition, zero coupon, pay-in-kind and delayed interest bonds
often do not pay interest until maturity. However, the Portfolios must recognize
imputed interest income and pay dividends to shareholders even though it has
received no cash. In some instances, the Portfolios may have to sell securities
to have sufficient cash to pay the dividends.

See Appendix A for risks associated with certain other investments.

12 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

MANAGEMENT OF THE PORTFOLIO

TRUSTEES

Janus Capital furnishes continuous advice and recommendations concerning the
Portfolios' investments. Janus Capital also furnishes certain administrative,
compliance and accounting services for the Portfolios, and may be reimbursed by
the Portfolios for its costs in providing those services. In addition, Janus
Capital employees serve as officers of the Trust and Janus Capital provides
office space for the Portfolios and pays the salaries, fees and expenses of all
Portfolio officers and those Trustees who are affiliated with Janus Capital.

INVESTMENT PERSONNEL
PORTFOLIO MANAGERS
JAMES P. CRAIG, III is Chief Investment Officer of Janus Capital. He is
Executive Vice President and portfolio manager of Growth Portfolio, which he has
managed since inception. Mr. Craig previously managed Balanced Portfolio from
September 1993 through April 1996 and has co-managed Janus Venture Fund since
February 1, 1997. Mr. Craig previously managed Janus Venture Fund from its
inception to December 1993 and Janus Balanced Fund from December 1993 to
December 1995. He holds a Bachelor of Arts in Business from the University of
Alabama and a Master of Arts in Finance from the Wharton School of the
University of Pennsylvania.

HELEN YOUNG HAYES is Executive Vice President and the portfolio manager of
Worldwide Growth Portfolio, which she has managed since its inception. Ms. Hayes
joined Janus Capital in 1987 and has managed or co-managed Janus Worldwide Fund,
Janus Overseas Fund and International Growth Portfolio since their inceptions.
She holds a Bachelor of Arts in Economics from Yale University and is a
Chartered Financial Analyst.

ASSISTANT PORTFOLIO MANAGERS
LAURENCE J. CHANG is assistant portfolio manager of Worldwide Growth Portfolio.
He is co-manager of International Growth Portfolio and Janus Overseas Fund. Mr.
Chang is assistant portfolio manager of Janus Worldwide Fund. He received an
undergraduate degree with honors in religion and philosophy from Dartmouth
College and a Master's Degree in Political Science from Stanford University. He
is a Chartered Financial Analyst.

DAVID C. DECKER is an assistant portfolio manager of the Growth Portfolio. He is
also an assistant portfolio manager of Janus Fund. He is Executive Vice
President and portfolio manager of Janus Special Situations Fund. Mr. Decker
received a Masters of Business Administration in Finance from the Fuqua School
of Business at Duke University and a Bachelor's Degree in Economics and
Political Science from Tufts University. He is a Chartered Financial Analyst.

BLAINE P. ROLLINS is an assistant portfolio manager of the Growth Portfolio. He
is also assistant portfolio manager of Janus Fund. He is Executive Vice
President and portfolio manager of Equity Income Portfolio, Balanced Portfolio
and Janus Equity Income Fund. He holds a Bachelor of Science in Finance from the
University of Colorado and is a Chartered Financial Analyst.

PERSONAL INVESTING
Janus Capital does not permit portfolio managers to purchase and sell securities
for their own accounts, except under the limited exceptions in Janus Capital's
policy governing personal investing. Janus Capital's policy requires investment
and other personnel to conduct their personal investment activities in a manner
that Janus Capital believes is not detrimental to the Portfolio or Janus
Capital's other advisory clients. See the SAI for more detailed information.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 13
<PAGE>

following management fee schedule (expressed as an annual rate):

<TABLE>
<CAPTION>
AVERAGE DAILY
NET ASSETS ANNUAL RATE
FEE SCHEDULE OF PORTFOLIO PERCENTAGE(%)
- -----------------------------------------------------------------
<S> <C> <C>
Growth and First $300 Million 0.75
Worldwide Growth
Portfolios Next $200 Million 0.70
Over $500 Million 0.65
- -----------------------------------------------------------------
</TABLE>

Janus Capital has agreed to reduce each Portfolio's advisory fee to the extent
that such fee exceeds the effective rate of the Janus retail fund
corresponding to such Portfolio. Janus Capital may terminate this fee
reduction at any time upon at least 90 days' notice to the Trustees. The
effective rate is the advisory fee calculated by the corresponding retail fund
as of the last day of each calendar quarter (expressed as an annual rate). The
effective rates of Janus Fund and Janus Worldwide Fund were .65% and .65%,
respectively, for the quarter ended March 31, 1998.

Differences in the actual management fees incurred by the Portfolios are due
primarily to variances in the asset sizes of the corresponding retail funds. As
asset size increases, the annual rate of the management fee declines in
accordance with the above schedule. In addition, the Shares of each Portfolio
incur expenses not assumed by Janus Capital, including transfer agent and
custodian fees and expenses, legal and auditing fees, printing and mailing costs
of sending reports and other information to existing shareholders, and
independent Trustees' fees and expenses.

The fee schedule for the Portfolios was effective July 1, 1997.

During the most recent fiscal year the Portfolios paid the following management
fees expressed as a percentage of average net assets: Growth Portfolio .65% and
Worldwide Growth Portfolio .66%.

OTHER SERVICE PROVIDERS
The following parties provide the Portfolios with administrative and other
services.

CUSTODIAN
State Street Bank and Trust Company
P.O. Box 0351
Boston, Massachusetts 02117-0351

TRANSFER AGENT
Janus Service Corporation
P.O. Box 173375
Denver, Colorado 80217-3375

Janus Service Corporation is a wholly-owned subsidiary of Janus Capital.

Each Portfolio currently offers two classes of Shares, one of which, the
Institutional Shares, are offered pursuant to this Prospectus and are sold under
the name Janus Aspen Series. The Shares offered by this Prospectus are available
only in connection with investment in and payments under variable insurance
contracts as well as certain qualified retirement plans. Retirement Shares of
each Portfolio are offered by separate prospectus and are available only to
participant directed qualified plans using plan service providers that are
compensated for providing distribution and/or recordkeeping and other
administrative services provided to plan participants. Because the expenses of
each class may differ, the performance of each class is expected to differ. If
you would like additional information about the Retirement Shares, please call
1-800-525-0020.

SHAREHOLDER MEETINGS AND VOTING RIGHTS
The Trust does not intend to hold annual shareholder meetings. However, special
meetings may be called for a specific class or Portfolio or for the Trust as a
whole for purposes such as electing or removing Trustees, terminating or
reorganizing the Trust, changing fundamental policies, or for any other purpose
requiring a shareholder vote under the 1940 Act. Separate votes are taken by
each class or Portfolio only if a matter affects or requires the vote of only
that class or Portfolio or the interest in the matter differs from the interest
of the other class or Portfolios of the Trust. As a shareholder, you are
entitled to one vote for each share that you own.

An insurance company issuing a variable contract invested in Shares of a
Portfolio will request voting instructions from variable contract holders. Under
current law, the insurance

14 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

company must vote all Shares held by the separate account in proportion to the
voting instructions received.

CONFLICTS OF INTEREST
Each Portfolio's Shares are available only to variable annuity and variable life
separate accounts of insurance companies that are unaffiliated with Janus
Capital and to certain qualified retirement plans. Retirement Shares of the
Portfolios (offered through a separate prospectus) are available to certain
participant directed qualified plans. Although the Portfolios do not currently
anticipate any disadvantages to policy owners arising out of the fact that each
Portfolio offers its shares to such entities, there is a possibility that a
material conflict may arise. The Trustees monitor events in order to identify
any anticipated disadvantages or material irreconcilable conflicts to determine
what action, if any, should be taken in response to such conflicts. If a
material disadvantage or conflict occurs, the Trustees may require one or more
insurance company separate accounts or plans to withdraw its investment in one
or more Portfolios or substitute shares of another Portfolio. If this occurs, a
Portfolio may be forced to sell securities at disadvantageous prices. In
addition, the Trustees may refuse to sell shares of any Portfolio to any
separate account or may suspend or terminate the offering of a Portfolio's
shares if such action is required by law or regulatory authority or is in the
best interests of the Portfolio's shareholders. It is possible that a qualified
plan investing in the Retirement Shares of the Portfolios could lose its
qualified plan status under the Internal Revenue Code, which could have adverse
tax consequences on insurance company separate accounts investing in the Shares.
Janus Capital intends to monitor such qualified plans and the Portfolios may
discontinue sales to a qualified plan and require plan participants with
existing investments in the Retirement Shares to redeem those investments if a
plan loses (or in the opinion of Janus Capital is at risk of losing) its
qualified plan status.

THE VALUATION OF SHARES
The NAV of the Shares of a Portfolio is determined at the close of the regular
trading session of the New York Stock Exchange (the "NYSE") (normally 4:00 p.m.,
New York time) each day that the NYSE is open. NAV per Share is determined by
dividing the total value of the securities and other assets, less liabilities,
by the total number of Shares outstanding.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 15
<PAGE>

DISTRIBUTIONS AND TAXES

DISTRIBUTIONS
TO AVOID TAXATION OF THE PORTFOLIOS, THE INTERNAL REVENUE CODE REQUIRES EACH
PORTFOLIO TO DISTRIBUTE NET INCOME AND ANY NET GAINS REALIZED ON ITS INVESTMENTS
ANNUALLY. ORDINARY INCOME FROM DIVIDENDS AND INTEREST AND ANY NET REALIZED
SHORT-TERM GAINS ARE PAID TO SHAREHOLDERS AS ORDINARY INCOME DIVIDENDS. NET
REALIZED LONG-TERM GAINS, IF ANY, ARE PAID TO SHAREHOLDERS AS CAPITAL GAINS
DISTRIBUTIONS. EACH CLASS OF EACH PORTFOLIO MAKES SEMIANNUAL DISTRIBUTIONS IN
JUNE AND DECEMBER OF SUBSTANTIALLY ALL OF ITS INVESTMENT INCOME AND AN ANNUAL
DISTRIBUTION IN JUNE OF ITS NET REALIZED GAINS, IF ANY. ALL DIVIDENDS AND
CAPITAL GAINS DISTRIBUTIONS FROM SHARES OF A PORTFOLIO WILL BE AUTOMATICALLY
REINVESTED INTO ADDITIONAL SHARES OF THAT PORTFOLIO.

HOW DISTRIBUTIONS AFFECT NAV
Distributions are paid to shareholders as of the record date of the distribution
of a Portfolio, regardless of how long the shares have been held. Undistributed
income and realized gains are included in the daily NAV of a Portfolio's Shares.
The Share price of the Portfolio drops by the amount of the distribution, net of
any subsequent market fluctuations. For example, assume that on December 31,
Shares of the Growth Portfolio declared a dividend in the amount of $0.25 per
share. If the price of Growth Portfolio's Shares was $10.00 on December 30, the
Share price on December 31 would be $9.75, barring market fluctuations.

16 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

SHAREHOLDER'S GUIDE

PURCHASES
Purchases of Shares may be made only by the separate accounts of insurance
companies for the purpose of funding variable insurance contracts or by
qualified plans. Refer to the prospectus of the appropriate insurance company's
separate account or your plan documents for information on how to invest in the
Shares of each Portfolio.

Each Portfolio reserves the right to reject any specific purchase order.
Purchase orders may be refused if, in Janus Capital's opinion, they are of a
size that would disrupt the management of a Portfolio. Any Portfolio may
discontinue sales of its shares if management believes that a substantial
further increase may adversely affect the Portfolio's ability to achieve its
investment objective. In such event, however, it is anticipated that existing
policy owners and plan participants invested in that Portfolio would be
permitted to continue to authorize investment in such Portfolio and to reinvest
any dividends or capital gains distributions.

Shares of each Portfolio may be redeemed on any business day. Redemptions are
processed at the NAV next calculated after receipt and acceptance of the
redemption order by the Portfolio. Redemption proceeds will normally be wired to
the participating insurance company the business day following receipt of the
redemption order, but in no event later than seven days after receipt of such
order.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 17
<PAGE>

APPENDIX A

GLOSSARY OF INVESTMENT TERMS

This glossary provides a more detailed description of some of the types of
securities and other instruments in which the Portfolios may invest. The
Portfolios may invest in these instruments to the extent permitted by its
investment objective and policies. The Portfolios are not limited by this
discussion and may invest in any other types of instruments not precluded by the
policies discussed elsewhere in this Prospectus. Please refer to the SAI for a
more detailed discussion of certain instruments.

CONVERTIBLE SECURITIES are preferred stocks or bonds that pay a fixed dividend
or interest payment and are convertible into common stock at a specified price
or conversion ratio.

MORTGAGE- AND ASSET-BACKED SECURITIES are shares in a pool of mortgages or other
debt. These securities are generally pass-through securities, which means that
principal and interest payments on the underlying securities (less servicing
fees) are passed through to shareholders on a pro rata basis. These securities
involve prepayment risk, which is the risk that the underlying mortgages or
other debt may be refinanced or paid off prior to their maturities during
periods of declining interest rates. In that case, a portfolio manager may have
to reinvest the proceeds from the securities at a lower rate. Potential market
gains on a security subject to prepayment risk may be more limited than
potential market gains on a comparable security that is not subject to
prepayment risk.

18 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

RULE 144A SECURITIES are securities that are not registered for sale to the
general public under the Securities Act of 1933, but that may be resold to
certain institutional investors.

STANDBY COMMITMENTS are obligations purchased by a Portfolio from a dealer that
give the Portfolio the option to sell a security to the dealer at a specified
price.

WHEN-ISSUED, DELAYED DELIVERY AND FORWARD TRANSACTIONS generally involve the
purchase of a security with payment and delivery at some time in the
future - i.e., beyond normal settlement. The Portfolios do not earn interest on
such securities until settlement and bears the risk of market value fluctuations
between the purchase and settlement dates. New issues of stocks and bonds,
private placements and U.S. government securities may be sold in this manner.

FUTURES CONTRACTS are contracts that obligate the buyer to receive and the
seller to deliver an instrument or money at a specified price on a specified
date. The Portfolios may buy and sell futures contracts on foreign currencies,
securities and financial indices including interest rates or an index of U.S.
government, foreign government, equity or fixed-income securities. They may also
buy options on futures contracts. An option on a futures contract gives the
buyer the right, but not the obligation, to buy or sell a futures contract at a
specified price on or before a specified date. Futures contracts and options on
futures are standardized and traded on designated exchanges.

INTEREST RATE SWAPS involve the exchange by two parties of their respective
commitments to pay or receive interest (e.g., an exchange of floating rate
payments for fixed rate payments).

INVERSE FLOATERS are debt instruments whose interest rate bears an inverse
relationship to the interest rate on another instrument or index. For example,
upon reset the interest rate

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 19
<PAGE>

payable on a security may go down when the underlying index has risen. Certain
inverse floaters may have an interest rate reset mechanism that multiplies the
effects of change in the underlying index. Such mechanism may increase the
volatility of the security's market value.

20 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

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<PAGE>
JANUS ASPEN SERIES
PROSPECTUS
Growth Portfolio
Worldwide Growth Portfolio

[JANUS LOGO]

P.O. Box 173375 o Denver, CO 80217-3375 o 1-800-525-1068
(5/98)
<PAGE>

JANUS ASPEN SERIES
WORLDWIDE GROWTH PORTFOLIO

Prospectus

MAY 1, 1998

Worldwide Growth Portfolio (the "Portfolio") is a diversified mutual fund that
seeks long-term growth of capital in a manner consistent with the preservation
of capital. The Portfolio pursues its objective by investing primarily in common
stocks of foreign and domestic issuers.

The Portfolio is a series of Janus Aspen Series (the "Trust") and currently
offers two classes of shares. The Institutional Shares are sold under the name
"Janus Aspen Series." The Trust is registered with the Securities and Exchange
Commission ("SEC") as an open-end management investment company. The
Institutional Shares of the Portfolio (the "Shares") are offered by this
prospectus in connection with investment in and payments under variable annuity
contracts and variable life insurance contracts (collectively "variable
insurance contracts"), as well as certain qualified retirement plans. Janus
Capital Corporation ("Janus Capital") serves as investment advisor to the
Portfolio. Janus Capital has been in the investment advisory business for over
27 years and currently manages approximately $80 billion in assets. The Trust
sells and redeems its Shares at net asset value without any sales charges,
commissions or redemption fees. Each variable insurance contract involves fees
and expenses not described in this Prospectus. See the accompanying contract
prospectus for information regarding contract fees and expenses and any
restrictions on purchases or allocations.

This Prospectus contains information about the Shares that a prospective
purchaser of a variable insurance contract or plan participant should consider
before allocating purchase payments or premiums to the Portfolio. It should be
read carefully in conjunction with the separate account prospectus of the
specific insurance product that accompanies this Prospectus and retained for
future reference. Additional information about the Shares is contained in a
Statement of Additional Information ("SAI") filed with the SEC. The SAI dated
May 1, 1997 is incorporated by reference into this Prospectus. Copies of the SAI
are available upon request and without charge by writing or calling your
insurance company or plan sponsor.

THESE SECURITIES HAVE NOT BEEN APPROVED BY THE SEC NOR HAS THE SEC PASSED ON THE
ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A
CRIMINAL OFFENSE.

THIS PROSPECTUS DOES NOT CONSTITUTE AN OFFER TO SELL SECURITIES IN ANY STATE OR
OTHER JURISDICTION TO ANY PERSON TO WHOM IT IS UNLAWFUL TO MAKE SUCH AN OFFER IN
SUCH STATE OR OTHER JURISDICTION.

JANUS ASPEN SERIES WORLDWIDE GROWTH PORTFOLIO PROSPECTUS MAY 1, 1998
<PAGE>

CONTENTS

<TABLE>
<S> <C>
THE PORTFOLIO AT A GLANCE
Brief description of the Portfolio.......................... 2
EXPENSE INFORMATION
The Portfolio's annual operating expenses................... 3

FINANCIAL HIGHLIGHTS -- A SUMMARY OF FINANCIAL DATA......... 4
PERFORMANCE TERMS
An explanation of performance terms......................... 5
THE PORTFOLIO IN DETAIL
Investment Objective and Policies........................... 6
General Portfolio Policies.................................. 7
Additional Risk Factors..................................... 8
MANAGEMENT OF THE PORTFOLIO
Investment Adviser and Investment Personnel................. 10
Personal Investing.......................................... 10
Management Expenses......................................... 10
Portfolio Transactions...................................... 11
Other Service Providers..................................... 11
Other Information........................................... 11
DISTRIBUTIONS AND TAXES
Distributions............................................... 13
Taxes....................................................... 13
SHAREHOLDER'S GUIDE
Purchases................................................... 14
Redemptions................................................. 14
Shareholder Communications.................................. 14
APPENDIX A
Glossary of Investment Terms................................ 15
</TABLE>

JANUS ASPEN SERIES WORLDWIDE GROWTH PORTFOLIO PROSPECTUS MAY 1, 1998 1
<PAGE>

PORTFOLIO AT A GLANCE

This section is designed to provide you with a brief overview of the Portfolio
and its investment emphasis. A more detailed discussion of the Portfolio's
investment objective and policies begins on page 5.

INVESTMENT OBJECTIVE:
The investment objective of the Portfolio is long-term growth of capital in a
manner consistent with the preservation of capital.

PRIMARY HOLDINGS:
A diversified portfolio that pursues its investment objective by investing
primarily in common stocks of foreign and domestic issuers.

SHAREHOLDER'S
INVESTMENT HORIZON:
The Portfolio is designed for long-term investors who seek growth of capital
only and who can tolerate the greater risks associated with investments in
common stocks. The Portfolio is not designed as a short-term trading vehicle and
should not be relied upon for short-term financial needs.

FUND ADVISER:
Janus Capital Corporation ("Janus Capital") serves as the Portfolio's investment
adviser. Janus Capital has been in the investment advisory business for over 27
years and currently manages approximately $80 billion in assets.

PORTFOLIO MANAGER:
Helen Young Hayes

ASSISTANT PORTFOLIO MANAGER:
Laurence J. Chang

PORTFOLIO INCEPTION:
September 1993

2 JANUS ASPEN SERIES WORLDWIDE GROWTH PORTFOLIO PROSPECTUS MAY 1, 1998
<PAGE>

EXPENSE INFORMATION

The following tables and example are designed to assist participants in
qualified plans that invest in the Shares of the Portfolio in understanding the
various costs and expenses that you will bear directly or indirectly as an
investor in the Shares. OWNERS OF VARIABLE INSURANCE CONTRACTS THAT INVEST IN
THE SHARES SHOULD REFER TO THE VARIABLE INSURANCE CONTRACT PROSPECTUS FOR A
DESCRIPTION OF COSTS AND EXPENSES, AS THE TABLES AND EXAMPLE DO NOT REFLECT
DEDUCTIONS AT THE SEPARATE ACCOUNT LEVEL OR CONTRACT LEVEL FOR ANY CHARGES THAT
MAY BE INCURRED UNDER A CONTRACT.

SHAREHOLDER TRANSACTION EXPENSES

ANNUAL OPERATING EXPENSES (after fee reductions)(1)
(expressed as a percentage of average net assets)

<TABLE>
<S> <C>
Management Fee 0.66%
Other Expenses 0.08%
-------------------------------------------------------------------------------------------------------
Total Operating Expenses 0.74%
-------------------------------------------------------------------------------------------------------
</TABLE>

(1) Management fees for Worldwide Growth Portfolio reflect a reduced fee
schedule effective July 1, 1997. The management fee for this Portfolio
reflects the new rate applied to net assets as of December 31, 1997. Other
expenses are based on the gross expenses of the Shares before expense offset
arrangements for the fiscal year ended December 31, 1997. The information
for Worldwide Growth Portfolio is net of fee reductions from Janus Capital.
Fee reductions for the Portfolio reduce the management fee to the level of
the corresponding Janus retail fund. Without such reductions, the Management
Fee, Other Expenses and Total Operating Expenses for the Shares would have
been 0.72%, 0.09% and 0.81%, respectively. Janus Capital may modify or
terminate the fee reductions at any time upon at least 90 days' notice to
the Trustees.

EXAMPLE

<TABLE>
<CAPTION>
- -------------------------------------------------------------------------------------------------------------
1 YEAR 3 YEARS 5 YEARS 10 YEARS
- -------------------------------------------------------------------------------------------------------------
<S> <C> <C> <C> <C>

Assume you invest $1,000, the Shares of the Portfolio return
5% annually and the Portfolio's expense ratio remains as
listed above. This example shows the operating expenses that
you would indirectly bear as an investor in the Shares of
the Portfolio. $ 8 $24 $41 $92
------------------------------------------------------------------------------------------------------------
</TABLE>

THE EXAMPLE SHOULD NOT BE CONSIDERED A REPRESENTATION OF PAST OR FUTURE RETURNS
OR EXPENSES WHICH MAY BE MORE OR LESS THAN THOSE SHOWN.

JANUS ASPEN SERIES WORLDWIDE GROWTH PORTFOLIO PROSPECTUS MAY 1, 1998 3
<PAGE>

FINANCIAL HIGHLIGHTS

Unless otherwise noted, the information below is for fiscal periods ending on
December 31st of each year. The accounting firm of Price Waterhouse LLP has
audited the Portfolio's financial statements since its inception. Their report
is included in the Portfolio's Annual Report, which is incorporated by reference
into the SAI. A DETAILED EXPLANATION OF THE FINANCIAL HIGHLIGHTS CAN BE FOUND ON
PAGE 4.

<TABLE>
<CAPTION>
INSTITUTIONAL SHARES 1997 1996 1995 1994 1993(1)
<S> <C> <C> <C> <C> <C>
- -----------------------------------------------------------------------------------------------------------------
1. NET ASSET VALUE, BEGINNING OF PERIOD $19.44 $15.31 $12.07 $11.89 $10.00
- -------------------------------------------------------------------------------------------------------------------------------
INCOME FROM INVESTMENT OPERATIONS:
2. Net investment income .16 .16 0.11 0.04 0.02
3. Net gains or (losses) on securities (both realized and
unrealized) 4.14 4.27 3.19 0.14 1.89
- -------------------------------------------------------------------------------------------------------------------------------
4. Total from investment operations 4.30 4.43 3.30 0.18 1.91
- -------------------------------------------------------------------------------------------------------------------------------
LESS DISTRIBUTIONS:
5. Dividends (from net investment income) (0.17) (0.17) (0.06) -- (0.01)
6. Dividends (in excess of net investment income) (.02) -- -- -- --
7. Tax return of capital distributions -- -- -- -- --
8. Distributions (from capital gains) (.16) (0.13) -- -- (0.01)
- -------------------------------------------------------------------------------------------------------------------------------
9. Total distributions (0.35) (0.30) (0.06) -- (0.02)
- -------------------------------------------------------------------------------------------------------------------------------
10. NET ASSET VALUE, END OF PERIOD $23.39 $19.44 $15.31 $12.07 $11.89
- -------------------------------------------------------------------------------------------------------------------------------
11. Total return* 22.15% 29.04% 27.37% 1.53% 19.10%
- -------------------------------------------------------------------------------------------------------------------------------
12. Net assets, end of period (in thousands) $1,576,548 $582,603 $108,563 $37,728 $4,856
13. Average net assets for the period (in thousands) $1,148,951 $304,111 $59,440 $22,896 $2,200
14. Ratio of gross expenses to average net assets** 0.74%(7) 0.80%(6) 0.90%(5) N/A N/A
15. Ratio of net expenses to average net assets** 0.74% 0.80% 0.87% 1.18%(2)(4) 0.25%(3)
16. Ratio of net investment income to average net assets** 0.67% 0.83% 0.95% 0.50% 0.84%
17. Portfolio turnover rate** 80% 62% 113% 217% 57%
18. Average commission rate $0.0337 $0.0345 N/A N/A N/A
- -------------------------------------------------------------------------------------------------------------------------------
</TABLE>

* Total return is not annualized for periods of less than one full year.
** Annualized for periods of less than one full year.
(1) September 13, 1993 (inception) to December 31, 1993.
(2) Commissions payable by the Portfolio for transactions effected by a
broker-dealer affiliated with Janus Capital were credited against the
Portfolio's operating expenses. The effect of such directed brokerage
arrangement was de minimis.
(3) The ratio was 2.71% before waiver of certain fees and voluntary reduction of
adviser's fees to the effective rate of Janus Worldwide Fund.
(4) The ratio was 1.49% before voluntary reduction of adviser's fees to the
effective rate of Janus Worldwide Fund.
(5) The ratio was 1.09% before voluntary reduction of adviser's fees to the
effective rate of Janus Worldwide Fund.
(6) The ratio was 0.91% before voluntary reduction of adviser's fees to the
effective rate of Janus Worldwide Fund.
(7) The ratio was 0.81% before voluntary reduction of adviser's fees to the
effective rate of Janus Worldwide Fund.

UNDERSTANDING THE
FINANCIAL HIGHLIGHTS

NET ASSET VALUE ("NAV") is the value of a single Share of the Portfolio. It is
computed by adding the value of all of the Portfolio's investments and other
assets, subtracting any liabilities and dividing the result by the number of
shares outstanding. The difference between line 1 and line 10 in the Financial
Highlights table represents the change in value of a Share of the Portfolio over
the fiscal period, but not its total return.

NET INVESTMENT INCOME is the per share amount of dividends and interest income
earned on securities held by the Portfolio, less Portfolio expenses. DIVIDENDS
(FROM NET INVESTMENT INCOME) are the per share amount that the Portfolio paid
from net investment income.

NET GAINS OR (LOSSES) ON SECURITIES is the per share increase or decrease in
value of the securities the Portfolio holds. A gain (or loss) is realized when
securities are sold. A gain (or loss) is unrealized when securities increase or
decrease in value but are not sold. DISTRIBUTIONS (FROM CAPITAL GAINS) are the
per share amount that the Portfolio paid from net realized gains.

4 JANUS ASPEN SERIES WORLDWIDE GROWTH PORTFOLIO PROSPECTUS MAY 1, 1998
<PAGE>

and distributions are reinvested at the NAV on the day of the distribution.

RATIO OF GROSS EXPENSES TO AVERAGE NET ASSETS is the total of the Portfolio's
operating expenses before expense offset arrangements divided by its average net
assets for the stated period. The Portfolios were not required to disclose the
ratio of gross expenses to average net assets prior to 1995. RATIO OF NET
EXPENSES TO AVERAGE NET ASSETS reflects reductions in a Portfolio's expenses
through the use of brokerage commissions and uninvested cash balances earning
interest or balance credits.

RATIO OF NET INVESTMENT INCOME TO AVERAGE NET ASSETS is the Portfolio's net
investment income divided by its average net assets for the stated period.

PORTFOLIO TURNOVER RATE is a measure of the amount of the Portfolio's buying and
selling activity. It is computed by dividing total purchases or sales, whichever
is less, by the average monthly market value of the Portfolio's securities.

AVERAGE COMMISSION RATE is the total of the Portfolio's agency commission paid
on equity securities trades divided by the number of shares purchased and sold.

PERFORMANCE TERMS

This section will help you understand various terms that are commonly used to
describe the Portfolio's performance. You may see references to these terms in
our newsletters or advertisements (or those published by participating insurance
companies) and in media articles. Newsletters and advertisements may include
comparisons of the Portfolio's performance to the performance of other mutual
funds, mutual fund averages or recognized stock market indices. The Portfolio
generally measures performance in terms of total return.

CUMULATIVE TOTAL RETURN represents the actual rate of return on an investment
for a specified period. The Financial Highlights table shows total return for a
single fiscal period. Cumulative total return is generally quoted for more than
one year (e.g., the life of the Portfolio). A cumulative total return does not
show interim fluctuations in the value of an investment.

AVERAGE ANNUAL TOTAL RETURN represents the average annual percentage change of
an investment over a specified period. It is calculated by taking the cumulative
total return for the stated period and determining what constant annual return
would have produced the same cumulative return. Average annual returns for more
than one year tend to smooth out variations in the Portfolio's return and are
not the same as actual annual results.

THE PORTFOLIO IMPOSES NO SALES OR OTHER CHARGES THAT WOULD AFFECT TOTAL RETURN
COMPUTATIONS. THE PORTFOLIO'S TOTAL RETURN FIGURES INCLUDE THE EFFECT OF
DEDUCTING THE PORTFOLIO'S EXPENSES, BUT MAY NOT INCLUDE CHARGES AND EXPENSES
ATTRIBUTABLE TO ANY PARTICULAR INSURANCE PRODUCT. PORTFOLIO PERFORMANCE FIGURES
ARE BASED UPON HISTORICAL RESULTS AND ARE NOT INTENDED TO INDICATE FUTURE
PERFORMANCE. INVESTMENT RETURNS AND NET ASSET VALUE WILL FLUCTUATE SO THAT
SHARES, WHEN REDEEMED, MAY BE WORTH MORE OR LESS THAN THEIR ORIGINAL COST.

THE PORTFOLIO IN DETAIL

This section takes a closer look at the Portfolio's investment objective,
policies and the securities in which it invests. Please carefully review the
"Additional Risk Factors" section of this Prospectus for a more detailed
discussion of the risks associated with certain investment techniques. Appendix
A contains a more detailed description of investment terms used throughout this
Prospectus. You should carefully consider your investment goals, time horizon
and risk tolerance before investing in the Portfolio.

The Portfolio's investment objective and policies are similar to those of Janus
Worldwide Fund, a retail fund managed by Janus Capital. Although it is
anticipated that the Portfolio and Janus Worldwide Fund will hold similar
securities, differences in asset size and cash flow needs as well as the
relative weightings of securities selections may result in differences in
investment performance. Expenses of the Portfolio and Janus Worldwide Fund are
expected to differ. The variable contract owner will also bear various
insurance-related costs at the insurance company level. You should review the
accompanying separate account prospectus for a summary of contract fees and
expenses.

Policies that are noted as "fundamental" cannot be changed without a shareholder
vote. All other policies, including the Portfolio's investment objective, are
not fundamental and may be changed by the Portfolio's Trustees without a
shareholder vote. You will be notified of any such changes that are material. If
there is a material change in the Portfolio's objective or policies, you should
consider whether the Portfolio remains an appropriate investment for your
variable insurance contract or qualified retirement plan.

THE PORTFOLIO IS DESIGNED FOR LONG-TERM INVESTORS WHO SEEK GROWTH OF CAPITAL
ONLY AND WHO CAN TOLERATE THE GREATER RISKS ASSOCIATED WITH COMMON STOCK
INVESTMENTS.

JANUS ASPEN SERIES WORLDWIDE GROWTH PORTFOLIO PROSPECTUS MAY 1, 1998 5
<PAGE>

WORLDWIDE GROWTH PORTFOLIO
Investment Objective:..........................................Growth of Capital
Primary Holdings:..................................................Common Stocks
Shareholder's Investment Horizon:......................................Long-Term

INVESTMENT OBJECTIVE
The investment objective of this Portfolio is long-term growth of capital in a
manner consistent with the preservation of capital. It is a diversified
portfolio that pursues its objective primarily through investments in common
stocks of foreign and domestic issuers. The Portfolio has the flexibility to
invest on a worldwide basis in companies and other organizations of any size,
regardless of country of organization or place of principal business activity.
The Portfolio normally invests in issuers from at least five different
countries, including the United States. The Portfolio may at times invest in
fewer than five countries or even a single country.

TYPES OF INVESTMENTS
The Portfolio invests primarily in common stocks of foreign and domestic
companies selected for their growth potential. The Portfolio may at times hold
substantial positions in cash equivalents or interest bearing securities. See
"General Portfolio Policies" on page 7. The Portfolio may invest to a lesser
degree in other types of securities including preferred stocks, warrants,
convertible securities and debt securities when its portfolio manager perceives
an opportunity for capital growth from such securities or to receive a return on
idle cash. Some securities that the Portfolio purchases may be on a when-issued,
delayed delivery or forward commitment basis. The Portfolio may invest up to 25%
of its assets in mortgage- and asset-backed securities, up to 10% of its assets
in zero coupon, pay-in-kind and step coupon securities, and without limit in
indexed/structured securities. The Portfolio will not invest 35% or more of its
assets in high-yield/high-risk securities.

The Portfolio is committed to foreign investing and may invest without limit in
foreign equity and debt securities. The Portfolio may invest directly in foreign
securities denominated in a foreign currency and not publicly traded in the
United States. Other ways of investing in foreign securities include depositary
receipts or shares, and passive foreign investment companies ("PFICs"). The
Portfolio may use futures, options and other derivatives for hedging purposes or
for non-hedging purposes such as seeking to enhance return. See "Additional Risk
Factors" on page 8 for a discussion of the risks associated with foreign
investing and derivatives.

THE FOLLOWING QUESTIONS ARE DESIGNED TO HELP YOU BETTER UNDERSTAND AN INVESTMENT
IN THE PORTFOLIO.

Q: HOW ARE COMMON STOCKS SELECTED?
A: The Portfolio invests substantially all of its assets in common stocks to
the extent the portfolio manager believes that the relevant market
environment favors profitable investing in those securities. The portfolio
manager generally takes a "bottom up" approach to building the Portfolio. In
other words, she seeks to identify individual companies with earnings growth
potential that may not be recognized by the market at large. Although themes may
emerge in the Portfolio, securities are generally selected without regard to any
defined industry sector or other similarly defined selection procedure.
Realization of income is not a significant investment consideration. Any income
realized on the Portfolio's investments will be incidental to its objective.

Q: ARE THE SAME CRITERIA USED TO SELECT FOREIGN SECURITIES?
A: Generally, yes. The portfolio manager seeks companies that meet her
selection criteria, regardless of country of organization or place of
principal business activity. Foreign securities are generally selected on a
stock-by-stock basis without regard to any defined allocation among countries or
geographic regions. However, certain factors such as expected levels of
inflation, government policies influencing business conditions, the outlook for
currency relationships, and prospects for economic growth among countries,
regions or geographic areas may warrant greater consideration in selecting
foreign securities. See "Additional Risk Factors" on page 8.

Q: WHAT IS THE MAIN RISK OF INVESTING IN WORLDWIDE GROWTH PORTFOLIO?
A: Since the Portfolio usually invests heavily in common stocks, the
fundamental risk is that the value of the stocks the Portfolio holds might
decrease. Stock values may fluctuate in response to the activities of an
individual company or in response to general market and economic conditions.
Historically, common stocks have provided greater long-term returns and have
entailed greater short-term risks than other investment choices. Smaller or
newer issuers are more likely to realize more substantial growth as well as
suffer more significant losses than larger or more established issuers.
Investments in such companies can be both more volatile and more speculative.
See "Additional Risk Factors" on page 8.

Q: HOW DOES THE PORTFOLIO TRY TO REDUCE RISK?
A: Diversification of the Portfolio's assets reduces the effect of any single
holding on its overall portfolio value. The Portfolio may use futures,
options and other derivative instruments to protect its portfolio from movements
in securities' prices and interest rates. The Portfolio may also use a variety
of currency hedging techniques, including forward currency contracts, to

6 JANUS ASPEN SERIES WORLDWIDE GROWTH PORTFOLIO PROSPECTUS MAY 1, 1998
<PAGE>

manage exchange rate risk when investing directly in foreign markets. See
"Additional Risk Factors" on page 8. In addition, to the extent that the
Portfolio holds a larger cash position, it may not participate in market
declines to the same extent as if it remained more fully invested in common
stocks.

GENERAL PORTFOLIO POLICIES
In investing its assets, the Portfolio will follow the general policies listed
below. The percentage limitations included in these policies and elsewhere in
this Prospectus apply only at the time of purchase of the security. For example,
if the Portfolio exceeds a limit as a result of market fluctuations or the sale
of other securities, it will not be required to dispose of any securities.

CASH POSITION
When the Portfolio's manager believes that market conditions are not favorable
for profitable investing or when the portfolio manager is otherwise unable to
locate favorable investment opportunities, the Portfolio's investments may be
hedged to a greater degree and/or its cash or similar investments may increase.
In other words, the Portfolio does not always stay fully invested in stocks and
bonds. Cash or similar investments are a residual -- they represent the assets
that remain after the portfolio manager has committed available assets to
desirable investment opportunities. A larger hedged position and/or larger cash
position may serve as a means of preserving capital in unfavorable market
conditions.

Securities that the Portfolio may invest in as means of receiving a return on
idle cash include high-grade commercial paper, certificates of deposit,
repurchase agreements or other short-term debt obligations. The Portfolio may
also invest in money market funds (including funds managed by Janus Capital).
When the Portfolio is hedged or its investments in cash or similar investments
increase, it may not participate in stock or bond market advances or declines to
the same extent that it would if the Portfolio was not hedged or remained more
fully invested in stocks or bonds.

DIVERSIFICATION
The Investment Company Act of 1940 (the "1940 Act") classifies investment
companies as either diversified or nondiversified. The Portfolio qualifies as a
diversified fund under the 1940 Act and is subject to the following
diversification requirements:

- - As a fundamental policy, the Portfolio may not own more than 10% of the
outstanding voting shares of any issuer.

- - As a fundamental policy, with respect to 75% of its total assets, the
Portfolio will not purchase a security of any issuer (other than cash items
and U.S. government securities, as defined in the 1940 Act) if such purchase
would cause the Portfolio's holdings of that issuer to amount to more than 5%
of the Portfolio's total assets. The Portfolio will not invest more than 25%
of its total assets in a single issuer (other than U.S. government
securities).

INTERNAL REVENUE SERVICE (IRS) LIMITATIONS
In addition to the diversification requirements stated above, the Portfolio
intends to comply with the diversification requirements currently imposed by the
IRS on separate accounts of insurance companies as a condition of maintaining
the tax-deferred status of variable contracts. More specific information may be
contained in the participating insurance company's separate account prospectus.

INDUSTRY CONCENTRATION
As a fundamental policy, the Portfolio will not invest 25% or more of its total
assets in any particular industry (excluding U.S. government securities).

PORTFOLIO TURNOVER
The Portfolio generally intends to purchase securities for long-term investment
rather than short-term gains. However, short-term transactions may result from
liquidity needs, securities having reached a price or yield objective, changes
in interest rates or the credit standing of an issuer, or by reason of economic
or other developments not foreseen at the time of the initial investment
decision. Changes are made in the Portfolio whenever its portfolio manager
believes such changes are desirable. The portfolio turnover rate is generally
not a factor in making buy and sell decisions.

To a limited extent, the Portfolio may purchase securities in anticipation of
relatively short-term price gains. The Portfolio may also sell one security and
simultaneously purchase the same or comparable security to take advantage of
short-term differentials in bond yields or securities prices. Increased
portfolio turnover may result in higher costs for brokerage commissions, dealer
mark-ups and other transaction costs and may also result in taxable capital
gains.

ILLIQUID INVESTMENTS
The Portfolio may invest up to 15% of its net assets in illiquid investments,
including restricted securities or private placements that are not deemed to be
liquid by Janus Capital. If illiquid securities exceed 15% of the Portfolio's
net assets after the time of purchase, the Portfolio will take steps to reduce
in an orderly fashion its holdings of illiquid securities. An illiquid
investment is a security or other position that cannot be disposed of quickly in
the normal course of business. Some securities cannot be sold to the U.S. public
because of their terms or because of SEC regulations. Janus Capital will follow
guidelines established by the Trustees of the Trust ("Trustees") in making
liquidity determinations for Rule 144A securities and other securities,
including privately placed commercial paper and municipal lease obligations.

BORROWING AND LENDING
The Portfolio may borrow money and lend securities or other assets, as follows:

- - The Portfolio may borrow money for temporary or emergency purposes in amounts
up to 25% of its total assets.

- - The Portfolio may mortgage or pledge securities as collateral for borrowings
in amounts up to 15% of its net assets.

JANUS ASPEN SERIES WORLDWIDE GROWTH PORTFOLIO PROSPECTUS MAY 1, 1998 7
<PAGE>

- - As a fundamental policy, the Portfolio may lend securities or other assets if,
as a result, no more than 25% of its total assets would be lent to other
parties.

Under the terms of an exemptive order received from the SEC, the Portfolio may
borrow money from or lend money to other funds that permit such transactions and
for which Janus Capital serves as investment adviser. All such borrowing and
lending will be subject to the above percentage limits.

ADDITIONAL RISK FACTORS

FOREIGN SECURITIES
INVESTMENTS IN FOREIGN SECURITIES, INCLUDING THOSE OF FOREIGN GOVERNMENTS, MAY
INVOLVE GREATER RISKS THAN INVESTING IN COMPARABLE DOMESTIC SECURITIES.
SECURITIES OF SOME FOREIGN COMPANIES AND GOVERNMENTS MAY BE TRADED IN THE UNITED
STATES, BUT MANY FOREIGN SECURITIES ARE TRADED PRIMARILY IN FOREIGN MARKETS. THE
RISKS OF FOREIGN INVESTING INCLUDE:

- - CURRENCY RISK. The Portfolio may buy the local currency when it buys a foreign
currency denominated security and sell the local currency when it sells the
security. As long as the Portfolio holds a foreign security, its value will be
affected by the value of the local currency relative to the U.S. dollar. When
the Portfolio sells a foreign denominated security, its value may be worth
less in U.S. dollars even though the security increases in value in its home
country. U.S. dollar denominated securities of foreign issuers may also be
affected by currency risk.

- - POLITICAL AND ECONOMIC RISK. Foreign investments may be subject to heightened
political and economic risks, particularly in underdeveloped or developing
countries which may have relatively unstable governments and economies based
on only a few industries. In some countries, there is the risk that the
government may take over the assets or operations of a company or that the
government may impose taxes or limits on the removal of the Portfolio's assets
from that country. The Portfolio may invest in emerging market countries.
Emerging market countries involve greater risks such as immature economic
structures, national policies restricting investments by foreigners, and
different legal systems.

- - TRANSACTION COSTS. Transaction costs of buying and selling foreign securities,
including brokerage, tax and custody costs, are generally higher than those
involved in domestic transactions. Foreign securities purchased indirectly
(e.g., depositary receipts) are subject to many of the above risks, including
currency risk, because their values depend on the performance of a foreign
security denominated in its home currency.

INVESTMENTS IN SMALLER COMPANIES
SMALLER OR NEWER COMPANIES MAY SUFFER MORE SIGNIFICANT LOSSES AS WELL AS REALIZE
MORE SUBSTANTIAL GROWTH THAN LARGER OR MORE ESTABLISHED ISSUERS.

FUTURES, OPTIONS AND OTHER DERIVATIVE INSTRUMENTS
The Portfolio may enter into futures contracts on securities, financial indices
and foreign currencies and options on such contracts ("futures contracts") and
may invest in options on securities, financial indices and foreign currencies
("options"), forward contracts and interest rate swaps and swap-related products
(collectively "derivative instruments"). The Portfolio intends to use most
derivative instruments primarily to hedge against potential adverse movements in
securities prices, foreign currency markets or interest rates. To a limited
extent, the Portfolio may also use derivative instruments for non-hedging
purposes such as seeking to increase its income or otherwise seeking to enhance
return. Please refer to Appendix A to this Prospectus and the SAI for a more
detailed discussion of these instruments.

The use of derivative instruments exposes the Portfolio to additional investment
risks and transaction costs. Risks inherent in the use of derivative instruments
include:

- - the risk that interest rates, securities prices and currency markets will not
move in the direction that the portfolio manager anticipates;

- - imperfect correlation between the price of derivative instruments and
movements in the prices of the securities, interest rates or currencies being
hedged;

- - the fact that skills needed to use these strategies are different from those
needed to select portfolio securities;

8 JANUS ASPEN SERIES WORLDWIDE GROWTH PORTFOLIO PROSPECTUS MAY 1, 1998
<PAGE>

- - inability to close out certain hedged positions to avoid adverse tax
consequences;

- - leverage risk, that is, the risk that adverse price movements in an instrument
can result in a loss substantially greater than the Portfolio's initial
investment in that instrument (in some cases, the potential loss is
unlimited); and

- - particularly in the case of privately-negotiated instruments, the risk that
the counterparty will fail to perform its obligations, which could leave the
Portfolio worse off than if it had not entered into the position.

Although the Portfolio's manager believes the use of derivative instruments will
benefit the Portfolio, the Portfolio's performance could be worse than if the
Portfolio had not used such instruments if the portfolio manager's judgment
proves incorrect. When the Portfolio invests in a derivative instrument, it may
be required to segregate cash and other liquid assets or certain portfolio
securities with its custodian to "cover" the Portfolio's position. Assets
segregated or set aside generally may not be disposed of so long as the
Portfolio maintains the positions requiring segregation or cover. Segregating
assets could diminish the Portfolio's return due to the opportunity losses of
foregoing other potential investments with the segregated assets.

HIGH-YIELD/HIGH-RISK SECURITIES
HIGH-YIELD/HIGH-RISK SECURITIES (OR "JUNK" BONDS) ARE DEBT SECURITIES RATED
BELOW INVESTMENT GRADE BY THE PRIMARY RATING AGENCIES SUCH AS STANDARD & POOR'S
RATINGS SERVICES ("STANDARD & POOR'S") AND MOODY'S INVESTORS SERVICE, INC.
("MOODY'S").

Issuers of high-yield/high-risk securities are more vulnerable to real or
perceived economic changes (for instance, an economic downturn or prolonged
period of rising interest rates), political changes or adverse developments
specific to the issuer. Adverse economic, political or other developments may
impair the issuer's ability to service principal and interest obligations, to
meet projected business goals and to obtain additional financing, particularly
if the issuer is highly leveraged. In the event of a default, the Portfolio
would experience a reduction of its income and could expect a decline in the
market value of the defaulted securities.

The market prices of high-yield/high-risk securities structured as zero coupon
or pay-in-kind securities are generally affected to a greater extent by interest
rate changes and tend to be more volatile than securities which pay interest
periodically. In addition, zero coupon, pay-in-kind and delayed interest bonds
often do not pay interest until maturity. However, the Portfolio must recognize
imputed interest income and pay dividends to shareholders even though it has
received no cash. In some instances, the Portfolio may have to sell securities
to have sufficient cash to pay the dividends.

SHORT SALES
The Portfolio may engage in "short sales against the box." This technique
involves selling either a security that the Portfolio owns, or a security
equivalent in kind and amount that the Portfolio has the right to obtain, for
delivery at a specified date in the future. The Portfolio may enter into a short
sale against the box to hedge against anticipated declines in the market price
of portfolio securities. If the value of the securities sold short increases
prior to the scheduled delivery date, the Portfolio loses the opportunity to
participate in the gain.

SPECIAL SITUATIONS
The Portfolio may invest in "special situations" from time to time. A special
situation arises when, in the opinion of the Portfolio's manager, the securities
of a particular issuer will be recognized and appreciate in value due to a
specific development with respect to that issuer. Developments creating a
special situation might include, among others, a new product or process, a
technological breakthrough, a management change or other extraordinary corporate
event, or differences in market supply of and demand for the security.
Investment in special situations may carry an additional risk of loss in the
event that the anticipated development does not occur or does not attract the
expected attention.

See Appendix A for risks associated with certain other investments.

JANUS ASPEN SERIES WORLDWIDE GROWTH PORTFOLIO PROSPECTUS MAY 1, 1998 9
<PAGE>

MANAGEMENT OF
THE PORTFOLIO

TRUSTEES

The Trustees oversee the business affairs of the Trust and are responsible for
major decisions relating to the Portfolio's investment objective and policies.
The Trustees delegate the day-to-day management of the Portfolio to the officers
of the Trust and meet at least quarterly to review the Portfolio's investment
policies, performance, expenses and other business affairs.

INVESTMENT ADVISER
Janus Capital, 100 Fillmore Street, Denver, Colorado 80206-4928, is the
investment adviser to the Portfolio and is responsible for the day-to-day
management of the investment portfolio and other business affairs of the
Portfolio.

Janus Capital furnishes continuous advice and recommendations concerning the
Portfolio's investments. Janus Capital also furnishes certain administrative,
compliance and accounting services for the Portfolio, and may be reimbursed by
the Portfolio for its costs in providing those services. In addition, Janus
Capital employees serve as officers of the Trust and Janus Capital provides
office space for the Portfolio and pays the salaries, fees and expenses of all
Portfolio officers and those Trustees who are affiliated with Janus Capital.

Participating insurance companies that purchase the Portfolio's Shares may
perform certain administrative services relating to the Portfolio and Janus
Capital or the Portfolio may pay those companies for such services.

INVESTMENT PERSONNEL
PORTFOLIO MANAGERS
HELEN YOUNG HAYES is Executive Vice President and portfolio manager of the
Portfolio and co-manager of International Growth Portfolio which she has managed
or co-managed since inception. Ms. Hayes joined Janus Capital in 1987 and has
managed or co-managed Janus Worldwide Fund and Janus Overseas Fund since their
inceptions. She holds a Bachelor of Arts in Economics from Yale University and
is a Chartered Financial Analyst.

PERSONAL INVESTING
Janus Capital does not permit portfolio managers to purchase and sell securities
for their own accounts, except under the limited exceptions contained in Janus
Capital's policy governing personal investing. Janus Capital's policy requires
investment and other personnel to conduct their personal investment activities
in a manner that Janus Capital believes is not detrimental to the Portfolio or
Janus Capital's other advisory clients. See the SAI for more detailed
information.

MANAGEMENT EXPENSES
The Portfolio pays Janus Capital a management fee which is calculated daily. The
advisory agreement with the Portfolio spells out the management fee and other
expenses that the Portfolio must pay. The Portfolio is subject to the following
management fee schedule (expressed as an annual rate):

<TABLE>
<CAPTION>
AVERAGE DAILY
FEE NET ASSETS ANNUAL RATE
SCHEDULE OF PORTFOLIO PERCENTAGE(%)
- --------------------------------------------------------------------
<S> <C> <C>
Worldwide First $300 Million 0.75
Growth Next $200 Million 0.70
Portfolio Over $500 Million 0.65
- --------------------------------------------------------------------
</TABLE>

Janus Capital has agreed to reduce the Portfolio's advisory fee to the extent
that such fee exceeds the effective rate of Janus Worldwide Fund. Janus
Capital may terminate this fee reduction at any time upon at least 90 days'
notice to the Trustees. The effective rate is the advisory fee calculated by
Janus Worldwide Fund as of the last day of each calendar quarter (expressed as
an annual rate). The effective rate of Janus Worldwide Fund was .65% for the
quarter ended March 31, 1998.

As asset size increases, the annual rate of the management fee declines in
accordance with the above schedule. In addition, the Shares of the Portfolio
incur expenses not assumed by Janus Capital, including transfer agent and
custodian fees and expenses, legal and auditing fees, printing and mailing costs
of sending reports and other information to existing shareholders, and
independent Trustees' fees and expenses. The fee schedule for the Portfolio was
effective July 1, 1997.

10 JANUS ASPEN SERIES WORLDWIDE GROWTH PORTFOLIO PROSPECTUS MAY 1, 1998
<PAGE>

The management fee expressed as a percentage of average net assets paid by the
Worldwide Growth Portfolio during the most recent fiscal year was .66%.

PORTFOLIO TRANSACTIONS
Purchases and sales of securities on behalf of the Portfolio are executed by
broker-dealers selected by Janus Capital. Broker-dealers are selected on the
basis of their ability to obtain best price and execution for the Portfolio's
transactions and recognizing brokerage, research and other services provided to
the Portfolio and to Janus Capital. Janus Capital may consider sales of shares
of the Portfolios or other Janus funds by a broker-dealer or the recommendation
of a broker-dealer to its customers that they purchase a Portfolio's shares as a
factor in the selection of broker-dealers to execute portfolio transactions.
Janus Capital may also consider payments made by brokers effecting transactions
for the Portfolio i) to the Portfolio or ii) to other persons on behalf of the
Portfolio for services provided to the Portfolio for which it would be obligated
to pay. The Portfolio's Trustees have authorized Janus Capital to place
portfolio transactions on an agency basis with a broker-dealer affiliated with
Janus Capital. When transactions for the Portfolio are effected with that
broker-dealer, the commissions payable by the Portfolio are credited against
certain Portfolio operating expenses serving to reduce those expenses. The SAI
further explains the selection of broker-dealers.

OTHER SERVICE PROVIDERS
The following parties provide the Portfolio with administrative and other
services.

CUSTODIAN
State Street Bank and Trust Company
P.O. Box 0351
Boston, Massachusetts 02117-0351

TRANSFER AGENT
Janus Service Corporation
P.O. Box 173375
Denver, Colorado 80217-3375

Janus Service Corporation is a wholly-owned subsidiary of Janus Capital.

OTHER INFORMATION

ORGANIZATION
The Trust is a "mutual fund" that was organized as a Delaware business trust on
May 20, 1993. A mutual fund is an investment vehicle that pools money from
numerous investors and invests the money to achieve a specified objective. The
Trust consists of twelve separate series, one of which is offered by this
Prospectus.

The Portfolio currently offers two classes of Shares, one of which, the
Institutional Shares, are offered pursuant to this prospectus and are sold under
the name Janus Aspen Series. The Shares offered by this Prospectus are available
only in connection with investment in and payments under variable insurance
contracts as well as certain qualified retirement plans. Retirement Shares of
the Portfolio are offered by separate prospectus and are available only to
participant directed qualified plans using plan service providers that are
compensated for providing distribution and/or recordkeeping and other
administrative services provided to plan participants. Because the expenses of
each class may differ, the performance of each class is expected to differ. If
you would like additional information about the Retirement Shares, please call
1-800-525-0020.

SHAREHOLDER MEETINGS AND VOTING RIGHTS
The Trust does not intend to hold annual shareholder meetings. However, special
meetings may be called for the class or Portfolio or for the Trust as a whole
for purposes such as electing or removing Trustees, terminating or reorganizing
the Trust, changing fundamental policies, or for any other purpose requiring a
shareholder vote under the 1940 Act. Separate votes are taken by the class or
Portfolio only if a matter affects or requires the vote of only the class or
Portfolio or the interest of a class or Portfolio in the matter differs from the
interest of the other class or Portfolios of the Trust. As a shareholder, you
are entitled to one vote for each share that you own.

An insurance company issuing a variable contract invested in Shares of the
Portfolio will request voting instructions from variable contract holders. Under
current law, the insurance company must vote all Shares held by the separate
account in proportion to the voting instructions received.

CONFLICTS OF INTEREST
The Portfolio's Shares are available only to variable annuity and variable life
separate accounts of insurance companies that are unaffiliated with Janus
Capital and to certain qualified retirement plans. Retirement Shares of the
Portfolio (offered through a separate prospectus) are available to certain
participant directed qualified plans. Although the Portfolio does not currently
anticipate any disadvantages to policy owners arising out of the fact that it
offers its shares to such entities, there is a possibility that a material
conflict may arise. The Trustees monitor events in order to identify any
anticipated disadvantages or material irreconcilable conflicts that may arise
and to determine what action, if any, should be taken in response. If a material
disadvantage or conflict occurs, the Trustees may require one or more insurance
company separate accounts or plans to withdraw its investment in the Portfolio
or substitute shares of another portfolio of the Trust. If this occurs, the
Portfolio may be forced to sell securities at disadvantageous prices. In
addition, the Trustees may refuse to sell shares of the Portfolio to any
separate account or may suspend or terminate the offering of the Portfolio's
shares if such action is required by law or regulatory authority or is in the
best interests of the Portfolio's shareholders. It is possible that a qualified
plan investing in the Retirement Shares of the Portfolio could lose its
qualified plan status under the Internal Revenue Code, which could have adverse
tax consequences on insurance company separate accounts investing in the Shares.
Janus Capital intends to monitor such qualified plans and the Portfolio may
discontinue sales to a qualified plan and require plan participants
JANUS ASPEN SERIES WORLDWIDE GROWTH PORTFOLIO PROSPECTUS MAY 1, 1998 11
<PAGE>

with existing investments in the Retirement Shares to redeem those investments
if a plan loses (or in the opinion of Janus Capital is at risk of losing) its
qualified plan status.

MASTER/FEEDER OPTION
The Trust may in the future seek to achieve the Portfolio's investment objective
by investing all of the Portfolio's assets in another investment company having
the same investment objective and substantially the same investment policies and
restrictions as those applicable to the Portfolio. Unless otherwise required by
law, this policy may be implemented by the Trustees without shareholder
approval.

THE VALUATION OF SHARES
The NAV of the Shares of the Portfolio is determined at the close of the regular
trading session of the New York Stock Exchange (the "NYSE") (normally 4:00 p.m.,
New York time) each day that the NYSE is open. NAV per share is determined by
dividing the total value of the securities and other assets, less liabilities,
by the total number of shares outstanding.

12 JANUS ASPEN SERIES WORLDWIDE GROWTH PORTFOLIO PROSPECTUS MAY 1, 1998
<PAGE>

DISTRIBUTIONS AND TAXES

DISTRIBUTIONS
TO AVOID TAXATION OF THE PORTFOLIO, THE INTERNAL REVENUE CODE REQUIRES THE
PORTFOLIO TO DISTRIBUTE NET INCOME AND ANY NET GAINS REALIZED ON ITS INVESTMENTS
ANNUALLY. ORDINARY INCOME FROM DIVIDENDS AND INTEREST AND ANY NET REALIZED
SHORT-TERM GAINS ARE PAID TO SHAREHOLDERS AS ORDINARY INCOME DIVIDENDS. NET
REALIZED LONG-TERM GAINS, IF ANY, ARE PAID TO SHAREHOLDERS AS CAPITAL GAINS
DISTRIBUTIONS. EACH CLASS OF THE PORTFOLIO MAKES SEMIANNUAL DISTRIBUTIONS IN
JUNE AND DECEMBER OF SUBSTANTIALLY ALL OF ITS INVESTMENT INCOME AND AN ANNUAL
DISTRIBUTION IN JUNE OF ITS NET REALIZED GAINS, IF ANY. ALL DIVIDENDS AND
CAPITAL GAINS DISTRIBUTIONS FROM THE SHARES OF THE PORTFOLIO WILL BE
AUTOMATICALLY REINVESTED INTO ADDITIONAL SHARES OF THE PORTFOLIO.

HOW DISTRIBUTIONS AFFECT NAV
Distributions are paid to shareholders as of the record date of the distribution
of the Portfolio, regardless of how long the shares have been held.
Undistributed income and realized gains are included in the daily NAV of the
Portfolio's Shares. The Share price of the Portfolio drops by the amount of the
distribution, net of any subsequent market fluctuations. For example, assume
that on December 31, the Shares of the Portfolio declared a dividend in the
amount of $0.25 per share. If the price of the Portfolio's Share was $10.00 on
December 30, the Share price on December 31 would be $9.75, barring market
fluctuations.

TAXES
TAXES ON DISTRIBUTIONS
Because Shares of the Portfolio may be purchased only through variable insurance
contracts and qualified plans, it is anticipated that any income dividends or
capital gains distributions made by the Shares of the Portfolio will be exempt
from current taxation if left to accumulate within the variable insurance
contract or qualified plan. Generally, withdrawals from such contracts may be
subject to ordinary income tax and, if made before age 59 1/2, a 10% penalty
tax. The tax status of your investment in the Shares depends on the features of
the variable insurance contracts purchased from a participating insurance
company. Further information may be found in the prospectus of the separate
account offering such contract.

TAXATION OF THE PORTFOLIO
Dividends, interest and some gains received by the Portfolio on foreign
securities may be subject to withholding of foreign taxes. The Portfolio may
from year to year make the election permitted under section 853 of the Internal
Revenue Code to pass through such taxes to shareholders as a foreign tax credit.
If such an election is not made, any foreign taxes paid or accrued will
represent an expense to the Portfolio which will reduce its investment income.

The Portfolio does not expect to pay any federal income or excise taxes because
it intends to meet certain requirements of the Internal Revenue Code. In
addition, the Portfolio intends to qualify under the Internal Revenue Code with
respect to the diversification requirements related to the tax-deferred status
of insurance company separate accounts.

JANUS ASPEN SERIES WORLDWIDE GROWTH PORTFOLIO PROSPECTUS MAY 1, 1998 13
<PAGE>

SHAREHOLDER'S GUIDE

INVESTORS MAY NOT PURCHASE OR REDEEM SHARES OF THE PORTFOLIO DIRECTLY. SHARES
MAY BE PURCHASED OR REDEEMED ONLY THROUGH VARIABLE INSURANCE CONTRACTS OFFERED
BY THE SEPARATE ACCOUNTS OF PARTICIPATING INSURANCE COMPANIES OR THROUGH
QUALIFIED RETIREMENT PLANS. REFER TO THE PROSPECTUS FOR THE PARTICIPATING
INSURANCE COMPANY'S SEPARATE ACCOUNT OR YOUR PLAN DOCUMENTS FOR INSTRUCTIONS ON
PURCHASING OR SELLING OF VARIABLE INSURANCE CONTRACTS AND ON HOW TO SELECT THE
PORTFOLIO AS AN INVESTMENT OPTION FOR A CONTRACT OR A QUALIFIED PLAN.

PURCHASES
Purchases of Shares may be made only by the separate accounts of insurance
companies for the purpose of funding variable insurance contracts or by
qualified plans. Refer to the prospectus of the appropriate insurance company's
separate account or your plan documents for information on how to invest in the
Shares of the Portfolio.

All investments in the Portfolio are credited to a participating insurance
company's separate account or a qualified plan immediately upon acceptance of
the investment by the Portfolio. Investments will be processed at the NAV next
determined after an order is received and accepted by the Portfolio.

The Portfolio reserves the right to reject any specific purchase order. Purchase
orders may be refused if, in Janus Capital's opinion, they are of a size that
would disrupt the management of the Portfolio. The Portfolio may discontinue
sales of its shares if management believes that a substantial further increase
may adversely affect the Portfolio's ability to achieve its investment
objective. In such event, however, it is anticipated that existing policy owners
and plan participants invested in the Portfolio would be permitted to continue
to authorize investment in the Portfolio and to reinvest any dividends or
capital gains distributions.

Shares of the Portfolio may be redeemed on any business day. Redemptions are
processed at the NAV next calculated after receipt and acceptance of the
redemption order by the Portfolio. Redemption proceeds will normally be wired to
the participating insurance company the business day following receipt of the
redemption order, but in no event later than seven days after receipt of such
order.

SHAREHOLDER COMMUNICATIONS
Shareholders will receive annual and semiannual reports including the financial
statements of the Shares of the Portfolio. Each report will show the investments
owned by the Portfolio and the market values thereof, as well as other
information about the Portfolio and its operations. The Trust's fiscal year ends
December 31.

14 JANUS ASPEN SERIES WORLDWIDE GROWTH PORTFOLIO PROSPECTUS MAY 1, 1998
<PAGE>

APPENDIX A

GLOSSARY OF INVESTMENT TERMS
This glossary provides a more detailed description of some of the types of
securities and other instruments in which the Portfolio may invest. The
Portfolio may invest in these instruments to the extent permitted by its
investment objective and policies. The Portfolio is not limited by this
discussion and may invest in any other types of instruments not precluded by the
policies discussed elsewhere in this Prospectus. Please refer to the SAI for a
more detailed discussion of certain instruments.

COMMERCIAL PAPER is a short-term debt obligation with a maturity ranging from 1
to 270 days issued by banks, corporations and other borrowers to investors
seeking to invest idle cash. The Portfolio may purchase commercial paper issued
under Section 4(2) of the Securities Act of 1933.

CONVERTIBLE SECURITIES are preferred stocks or bonds that pay a fixed dividend
or interest payment and are convertible into common stock at a specified price
or conversion ratio.

MORTGAGE- AND ASSET-BACKED SECURITIES are shares in a pool of mortgages or other
debt. These securities are generally pass-through securities, which means that
principal and interest payments on the underlying securities (less servicing
fees) are passed through to shareholders on a pro rata basis. These securities
involve prepayment risk, which is the risk that the underlying mortgages or
other debt may be refinanced or paid off prior to their maturities during
periods of declining interest rates. In that case, a portfolio manager may have
to reinvest the proceeds from the securities at a lower rate. Potential market
gains on a security subject to prepayment risk may be more limited than
potential market gains on a comparable security that is not subject to
prepayment risk.

PASSIVE FOREIGN INVESTMENT COMPANIES (PFICS) are any foreign corporations which
generate certain amounts of passive income or hold certain amounts of assets for
the production of passive income. Passive income includes dividends, interest,
royalties, rents and annuities. To avoid taxes and interest that the Portfolio
must pay if these investments are profitable, the Portfolio may make various
elections permitted by the tax laws. These elections could require that the
Portfolio recognize taxable income, which in turn must be distributed, before
the securities are sold and before cash is received to pay the distributions.

REPURCHASE AGREEMENTS involve the purchase of a security by the Portfolio and a
simultaneous agreement by the seller (generally a bank or dealer) to repurchase
the security from the Portfolio at a specified date or upon demand. This
technique offers a method of earning income on idle cash. These securities
involve the risk that the seller will fail to repurchase the security, as
agreed. In that case, the Portfolio will bear the risk of market value
fluctuations until the security can be sold and may encounter delays and incur
costs in liquidating the security.

REVERSE REPURCHASE AGREEMENTS involve the sale of a security by the Portfolio to
another party (generally a bank or dealer) in return for cash and an agreement
by the Portfolio to buy the security back at a specified price and time. This
technique will be used primarily to provide cash to satisfy unusually high
redemption requests, or for other temporary or emergency purposes.

JANUS ASPEN SERIES WORLDWIDE GROWTH PORTFOLIO PROSPECTUS MAY 1, 1998 15
<PAGE>

RULE 144A SECURITIES are securities that are not registered for sale to the
general public under the Securities Act of 1933, but may be resold to certain
institutional investors.

STANDBY COMMITMENTS are obligations purchased by a Portfolio from a dealer that
give the Portfolio the option to sell a security to the dealer at a specified
price.

WHEN-ISSUED, DELAYED DELIVERY AND FORWARD TRANSACTIONS generally involve the
purchase of a security with payment and delivery at some time in the
future -- i.e., beyond normal settlement. The Portfolio does not earn interest
on such securities until settlement and bear the risk of market value
fluctuations between the purchase and settlement dates. New issues of stocks and
bonds, private placements and U.S. government securities may be sold in this
manner.

ZERO COUPON BONDS are debt securities that do not pay interest at regular
intervals, but are issued at a discount from face value. The discount
approximates the total amount of interest the security will accrue from the date
of issuance to maturity. The market value of securities generally fluctuates
more in response to changes in interest rates than interest-paying securities of
comparable securities.

II. FUTURES, OPTIONS
AND OTHER DERIVATIVES
FORWARD CONTRACTS are contracts to purchase or sell a specified amount of a
financial instrument for an agreed upon price at a specified time. Forward
contracts are not currently exchange traded and are typically negotiated on an
individual basis. The Portfolio may enter into forward currency contracts to
hedge against declines in the value of securities denominated in, or whose value
is tied to, a currency other than the U.S. dollar or to reduce the impact of
currency appreciation on purchases of such securities. It may also enter into
forward contracts to purchase or sell securities or other financial indices.

FUTURES CONTRACTS are contracts that obligate the buyer to receive and the
seller to deliver an instrument or money at a specified price on a specified
date. The Portfolio may buy and sell futures contracts on foreign currencies,
securities and financial indices including interest rates or an index of U.S.
government, foreign government, equity or fixed-income securities. The Portfolio
may also buy options on futures contracts. An option on a futures contract gives
the buyer the right, but not the obligation, to buy or sell a futures contract
at a specified price on or before a specified date. Futures contracts and
options on futures are standardized and traded on designated exchanges.

INDEXED/STRUCTURED SECURITIES are typically short- to intermediate-term debt
securities whose value at maturity or interest rate is linked to currencies,
interest rates, equity securities, indices, commodity prices or other financial
indicators. Such securities may be positively or negatively indexed (i.e., their
value may increase or decrease if the reference index or instrument
appreciates). Indexed/structured securities may have return characteristics
similar to direct investments in the underlying instruments and may be more
volatile than the underlying instruments. The Portfolio bears the market risk of
an investment in the underlying instruments, as well as the credit risk of the
issuer.

INTEREST RATE SWAPS involve the exchange by two parties of their respective
commitments to pay or receive interest (e.g., an exchange of floating rate
payments for fixed rate payments).

INVERSE FLOATERS are debt instruments whose interest rate bears an inverse
relationship to the interest rate on another

16 JANUS ASPEN SERIES WORLDWIDE GROWTH PORTFOLIO PROSPECTUS MAY 1, 1998
<PAGE>

OPTIONS are the right, but not the obligation, to buy or sell a specified amount
of securities or other assets on or before a fixed date at a predetermined
price. The Portfolio may purchase and write put and call options on securities,
securities indices and foreign currencies.

JANUS ASPEN SERIES WORLDWIDE GROWTH PORTFOLIO PROSPECTUS MAY 1, 1998 17
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JANUS ASPEN SERIES
PROSPECTUS
Worldwide Growth Portfolio

[JANUS LOGO]

P.O. Box 173375 o Denver, CO 80217-3375 o 1-800-525-1068
(5/98)
<PAGE>

JANUS ASPEN SERIES

Prospectus

MAY 1, 1998

This Prospectus contains information about the Shares that a prospective
purchaser of a variable insurance contract or plan participant should consider
before allocating purchase payments or premiums to the Portfolio. It should be
read carefully in conjunction with the separate account prospectus of the
specific insurance product that accompanies this Prospectus and retained for
future reference. Additional information about the Shares is contained in a
Statement of Additional Information ("SAI") filed with the SEC. The SAI dated
May 1, 1998 is incorporated by reference into this Prospectus. Copies of the SAI
are available upon request and without charge by writing or calling your
insurance company or plan participant.

FLEXIBLE INCOME PORTFOLIO MAY INVEST ALL OF ITS ASSETS IN HIGH-YIELD CORPORATE
DEBT SECURITIES, COMMONLY KNOWN AS "JUNK BONDS." SEE "ADDITIONAL RISK FACTORS"
ON PAGE 11 FOR THE RISKS ASSOCIATED WITH INVESTING IN THESE SECURITIES.

THESE SECURITIES HAVE NOT BEEN APPROVED BY THE SEC NOR HAS THE SEC PASSED ON THE
ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A
CRIMINAL OFFENSE.

THIS PROSPECTUS DOES NOT CONSTITUTE AN OFFER TO SELL SECURITIES IN ANY STATE OR
OTHER JURISDICTION TO ANY PERSON TO WHOM IT IS UNLAWFUL TO MAKE SUCH AN OFFER IN
SUCH STATE OR OTHER JURISDICTION.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
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CONTENTS

<TABLE>
<S> <C>
THE PORTFOLIOS AT A GLANCE
Brief description of the Portfolios......................... 2
EXPENSE INFORMATION
Each Portfolio's annual operating expenses.................. 3
Financial Highlights - a summary of financial data.......... 4
PERFORMANCE TERMS
An explanation of performance terms......................... 6
THE PORTFOLIOS IN DETAIL
Investment Objectives and Policies.......................... 7
General Portfolio Policies.................................. 10
Additional Risk Factors..................................... 11
MANAGEMENT OF THE PORTFOLIOS
Investment Adviser and Investment Personnel................. 14
Personal Investing.......................................... 14
Management Expenses and Expense Limits...................... 14
Portfolio Transactions...................................... 15
Other Service Providers..................................... 15
Other Information........................................... 15
DISTRIBUTIONS AND TAXES
Distributions............................................... 17
Taxes....................................................... 17
SHAREHOLDER'S GUIDE
Purchases................................................... 18
Redemptions................................................. 18
Shareholder Communications.................................. 18
APPENDIX A
Glossary of Investment Terms................................ 19
APPENDIX B
Explanation of Rating Categories............................ 22
</TABLE>

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 1
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PORTFOLIOS AT A GLANCE

FLEXIBLE INCOME PORTFOLIO
Focus: A diversified portfolio that seeks to maximize total return from a
combination of income and capital appreciation by investing in income-producing
securities.
Inception: September 1993
Manager: Ronald V. Speaker

2 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
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EXPENSE INFORMATION

SHAREHOLDER TRANSACTION EXPENSES (applicable to each Portfolio)

ANNUAL OPERATING EXPENSES (after fee reductions)(1)
(expressed as a percentage of average net assets)

<TABLE>
<CAPTION>
- ----------------------------------------------------------------------------------------------------------------------
MANAGEMENT FEE OTHER EXPENSES TOTAL OPERATING EXPENSES
- ----------------------------------------------------------------------------------------------------------------------
<S> <C> <C> <C>

Worldwide Growth Portfolio 0.66% 0.08% 0.74%
Flexible Income Portfolio 0.65% 0.10% 0.75%
- ----------------------------------------------------------------------------------------------------------------------
</TABLE>

(1) Management fees for the Worldwide Growth Portfolio reflect a reduced fee
schedule effective July 1, 1997. The management fee for this Portfolio
reflects the new rate applied to net assets as of December 31, 1997. Other
expenses are based on the gross expenses of the Shares before expense offset
arrangements for the fiscal year ended December 31, 1997. The information
for Worldwide Growth Portfolio is net of fee reductions from Janus Capital.
Fee reductions for the Portfolio reduce the management fee to the level of
the corresponding Janus retail fund. Without such reductions, the Management
Fee, Other Expenses and Total Operating Expenses for Worldwide Growth
Portfolio would have been 0.72%, 0.09% and 0.81%, respectively. Janus
Capital may modify or terminate the fee reductions at any time upon at least
90 days' notice to the Trustees.

Worldwide Growth Portfolio $8 $24 $41 $92
Flexible Income Portfolio $8 $24 $42 $93
- ----------------------------------------------------------------------------------------------------------------
</TABLE>

THE EXAMPLE SHOULD NOT BE CONSIDERED A REPRESENTATION OF PAST OR FUTURE RETURNS
OR EXPENSES WHICH MAY BE MORE OR LESS THAN THOSE SHOWN.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 3
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FINANCIAL HIGHLIGHTS

Unless otherwise noted, the information below is for fiscal periods ending on
December 31st of each year. The accounting firm of Price Waterhouse LLP has
audited the Portfolios' financial statements since their inception. Their report
is included in the Portfolios' Annual Report, which is incorporated by reference
into the SAI. A DETAILED EXPLANATION OF THE FINANCIAL HIGHLIGHTS CAN BE FOUND ON
PAGE 5.
<TABLE>
<CAPTION>
WORLDWIDE GROWTH PORTFOLIO
INSTITUTIONAL SHARES 1997 1996 1995 1994 1993(1)
- -------------------------------------------------------------------------------------------------
<C> <S> <C> <C> <C> <C> <C>
1. Net asset value, beginning
of period $19.44 $15.31 $12.07 $11.89 $10.00
- -------------------------------------------------------------------------------------------------
INCOME FROM INVESTMENT
OPERATIONS:
2. Net investment income .16 .16 .11 .04 .02
3. Net gains or (losses) on
securities (both realized
and unrealized) 4.14 4.27 3.19 .14 1.89
- -------------------------------------------------------------------------------------------------
4. Total from investment
operations 4.30 4.43 3.30 .18 1.91
- -------------------------------------------------------------------------------------------------
LESS DISTRIBUTIONS:
5. Dividends (from net
investment income) (.17) (.17) (.06) -- (.01)
6. Dividends (in excess of net
investment income) (.02) -- -- -- --
7. Tax return of capital
distributions -- -- -- -- --
8. Distributions (from capital
gains) (.16) (.13) -- -- (.01)
- -------------------------------------------------------------------------------------------------
9. Total distributions (.35) (.30) (.06) -- (.02)
- -------------------------------------------------------------------------------------------------
10. Net asset value, end of
period $23.39 $19.44 $15.31 $12.07 $11.89
- -------------------------------------------------------------------------------------------------
11. Total return* 22.15% 29.04% 27.37% 1.53% 19.10%
- -------------------------------------------------------------------------------------------------
12. Net assets, end of period
(in thousands) $1,576,548 $582,603 $108,563 $37,728 $4,856
13. Average net assets for the
period (in thousands) $1,148,951 $304,111 $59,440 $22,896 $2,200
14. Ratio of gross expenses to
average net assets** 0.74%(7) 0.80%(6) 0.90%(5) N/A N/A
15. Ratio of net expenses to
average net assets** 0.74% 0.80% 0.87% 1.18%(2)(4) 0.25%(3)
16. Ratio of net investment
income to average net
assets** 0.67% 0.83% 0.95% 0.50% 0.84%
17. Portfolio turnover rate** 80% 62% 113% 217% 57%
18. Average commission rate $0.0337 $0.0345 N/A N/A N/A
- -------------------------------------------------------------------------------------------------

<CAPTION>
FLEXIBLE INCOME PORTFOLIO
INS 1997 1996 1995 1994 1993(1)

- --------------------------------------------------------------
<C> <C> <C> <C> <C> <C>
1.
$11.24 $11.11 $9.48 $9.97 $10.00
- --------------------------------------------------------------

2. .67 .74 .53 .47 .11
3.

.62 .24 1.70 (.56) (.04)
- --------------------------------------------------------------
4.
1.29 .98 2.23 (.09) .07
- --------------------------------------------------------------

5.
(.64) (.72) (.60) (.40) (.10)
6.
-- -- -- -- --
7.
-- -- -- --
8.
(.11) (.13) -- -- --
- --------------------------------------------------------------
9. (.75) (.85) (.60) (.40) (.10)
- --------------------------------------------------------------
10.
$11.78 $11.24 $11.11 $9.48 $9.97
- --------------------------------------------------------------
11. 11.76% 9.19% 23.86% (0.91%) 0.70%
- --------------------------------------------------------------
12.
$54,098 $25,315 $10,831 $1,924 $538
13.
$36,547 $17,889 $5,556 $1,636 $497
14.
0.75% 0.84% 1.07% N/A N/A
15.
0.75% 0.83% 1.00% 1.00%(4) 1.00%(3)
16.

6.90% 7.31% 7.46% 5.49% 3.77%
17. 119% 250% 236% 234% 508%
18. N/A N/A N/A N/A N/A
- --------------------------------------------------------------
</TABLE>

* Total return not annualized for periods of less than one year.
** Annualized for periods of less than one full year.
(1) September 13, 1993 (inception) to December 31, 1993.
(2) Commissions payable by the Portfolio for transactions effected by a
broker-dealer affiliated with Janus Capital were credited against the
Portfolio's operating expenses. The effect of such directed brokerage
arrangement was de minimis.
(3) The ratio was 2.71% and 5.27%, respectively, for Worldwide Growth and
Flexible Income Portfolios before waiver of certain fees and/or voluntary
reduction of adviser's fees to the effective rate of the corresponding Janus
retail fund.
(4) The ratio was 1.49% and 1.35%, respectively, for Worldwide Growth and
Flexible Income Portfolios before waiver of certain fees and/or voluntary
reduction of adviser's fees to the effective rate of the corresponding Janus
retail fund.
(5) The ratio was 1.09% for Worldwide Growth Portfolio before voluntary
reduction of adviser's fees to the effective rate of Janus Worldwide Fund.
(6) The ratio was 0.91% for Worldwide Growth Portfolio before voluntary
reduction of adviser's fees to the effective rate of Janus Worldwide Fund.
(7) The ratio was 0.81% for Worldwide Growth Portfolio before voluntary
reduction of adviser's fees to the effective rate of Janus Worldwide Fund.

4 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
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UNDERSTANDING THE
FINANCIAL HIGHLIGHTS

This section is designed to help you better understand the information
summarized in the Financial Highlights table. The table contains important
historical operating information that may be useful in making your investment
decision or understanding how your investment has performed. The Portfolios'
Annual Report contains additional information about each Portfolio's
performance, including a comparison to an appropriate securities index. To
request a copy of the Annual Report, please call or write your insurance
company.

NET ASSET VALUE ("NAV") is the value of a single Share of a Portfolio. It is
computed by adding the value of all of a Portfolio's investments and other
assets, subtracting any liabilities and dividing the result by the number of
shares outstanding. The difference between line 1 and line 10 in the Financial
Highlights table represents the change in value of a Share of a Portfolio over
the fiscal period, but not its total return.

RATIO OF GROSS EXPENSES TO AVERAGE NET ASSETS is the total of a Portfolio's
operating expenses before expense offset arrangement divided by its average net
assets for the stated period. The Portfolios were not required to disclose the
ratio of gross expenses to average net assets prior to 1995. RATIO OF NET
EXPENSES TO AVERAGE NET ASSETS reflects reductions in a Portfolio's expenses
through the use of brokerage commissions and uninvested cash balances earning
interest or balance credits.

RATIO OF NET INVESTMENT INCOME TO AVERAGE NET ASSETS is a Portfolio's net
investment income divided by its average net assets for the stated period.

AVERAGE COMMISSION RATE is the total of a Portfolio's agency commission paid on
equity securities trades divided by the number of shares purchased and sold.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 5
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PERFORMANCE TERMS

This section will help you understand various terms that are commonly used to
describe a Portfolio's performance. You may see references to these terms in our
newsletters or advertisements (or those published by participating insurance
companies) and in media articles. Newsletters and advertisements may include
comparisons of a Portfolio's performance to the performance of other mutual
funds, mutual fund averages or recognized stock market indices. Worldwide Growth
Portfolio generally measures performance in terms of total return, while
Flexible Income Portfolio generally measures performance in terms of yield.

YIELD shows the rate of income the Shares earn on investments as a percentage of
the Share price. It is calculated by dividing a Portfolio's net investment
income for a 30-day period by the average number of shares entitled to receive
dividends and dividing the result by the Share's NAV per share at the end of the
30-day period. Yield does not include changes in NAV.

6 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
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THE PORTFOLIOS IN DETAIL

Each Portfolio has an investment objective and policies that are similar to
those of a Janus retail fund, as illustrated in the chart below. Although it is
anticipated that each Portfolio and its corresponding retail fund will hold
similar securities, differences in asset size and cash flow needs as well as the
relative weightings of securities selections may result in differences in
investment performance. Expenses of each Portfolio and its corresponding retail
fund are expected to differ. The variable contract owner will also bear various
insurance-related costs at the insurance company level. You should review the
accompanying separate account prospectus for a summary of contract fees and
expenses.

EACH OF THE PORTFOLIOS HAS A SIMILAR INVESTMENT
OBJECTIVE AND SIMILAR INVESTMENT POLICIES TO AN EXISTING JANUS RETAIL FUND.

Worldwide Growth Portfolio................................Janus Worldwide Fund
Flexible Income Portfolio...........................Janus Flexible Income Fund

WORLDWIDE GROWTH PORTFOLIO IS DESIGNED FOR LONG-TERM INVESTORS WHO SEEK GROWTH
OF CAPITAL ONLY AND WHO CAN TOLERATE THE GREATER RISKS ASSOCIATED WITH COMMON
STOCK INVESTMENTS.

TYPES OF INVESTMENTS
Worldwide Growth Portfolio invests primarily in common stocks of foreign and
domestic companies. The Portfolio may at times hold substantial positions in
cash equivalents or interest bearing securities. See "General Portfolio
Policies" on page 10. The Portfolio may invest to a lesser degree in other types
of securities including preferred stocks, warrants, convertible securities and
debt securities when its portfolio manager perceives an opportunity for capital
growth from such securities or to receive a return on idle cash. Some securities
that the Portfolio purchases may be on a when-issued, delayed delivery or
forward commitment basis. The Portfolio may invest up to 25% of its assets in
mortgage- and asset-backed securities, up to 10% of its assets in zero coupon,
pay-in-kind and step coupon securities, and without limit in indexed/structured
securities. The Portfolio will not invest 35% or more of its assets in
high-yield/high-risk securities.

The Portfolio may also invest without limit in foreign equity and debt
securities. The Portfolio may invest directly in foreign securities denominated
in a foreign currency and not publicly traded in the United States. Other ways
of investing in foreign securities include depositary receipts or shares, and
passive foreign investment companies ("PFICs"). The Portfolio may use futures,
options and other derivatives for hedging purposes or for non-hedging purposes
such as seeking to enhance return. See "Additional Risk Factors" on page 11 for
a discussion of the risks associated with foreign investing and derivatives.

THE FOLLOWING QUESTIONS ARE DESIGNED TO HELP YOU BETTER UNDERSTAND AN INVESTMENT
IN WORLDWIDE GROWTH PORTFOLIO.

Q: HOW ARE COMMON STOCKS SELECTED?

A: The Portfolio invests substantially all of its assets in common stocks to
the extent the portfolio manager believes that the relevant market
environment favors profitable investing in those securities. The Portfolio
manager generally takes a "bottom up" approach to building the portfolio. In
other words, she seeks to identify individual companies with earnings growth
potential that may not be recognized by the market at large. Although themes may
emerge in any Portfolio, securities are generally selected without regard to any
defined industry sector or other similarly defined selection procedure.
Realization of income is not a significant investment consideration. Any income
realized on the Portfolio's investments will be incidental to its objective.
JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 7
<PAGE>

Q: ARE THE SAME CRITERIA USED TO SELECT FOREIGN SECURITIES?

A: Generally, yes. The Portfolio manager seeks companies that meet her
selection criteria, regardless of country of organization or place of
principal business activity. Foreign securities are generally selected on a
stock-by-stock basis without regard to any defined allocation among countries or
geographic regions. However, certain factors such as expected levels of
inflation, government policies influencing business conditions, the outlook for
currency relationships, and prospects for economic growth among countries,
regions or geographic areas may warrant greater consideration in selecting
foreign securities. See "Additional Risk Factors" on page 11.

Q: WHAT IS THE MAIN RISK OF INVESTING IN WORLDWIDE GROWTH PORTFOLIO?

A: Since the Portfolio usually invests heavily in common stocks, the
fundamental risk is that the value of the stocks the portfolio holds might
decrease. Stock values may fluctuate in response to the activities of an
individual company or in response to general market and economic conditions.
Historically, common stocks have provided greater long-term returns and have
entailed greater short-term risks than other investment choices. Smaller or
newer issuers are more likely to realize more substantial growth as well as
suffer more significant losses than larger or more established issuers.
Investments in such companies can be both more volatile and more speculative.
See "Additional Risk Factors" on page 11.

Q: WHAT IS MEANT BY "MARKET CAPITALIZATION"?

A: Market capitalization is the most commonly used measure of the size and
value of a company. It is computed by multiplying the current market price
of a share of the company's stock by the total number of its shares outstanding.
Although Worldwide Growth Portfolio does not emphasize companies of any
particular size, a Portfolio with a larger asset base are more likely to invest
in larger, more-established issuers.

Q: HOW DOES THE PORTFOLIO TRY TO REDUCE RISK?

A: Diversification of the Portfolio's assets reduces the effect of any single
holding on its overall portfolio value. The Portfolio may also use
futures, options and other derivative instruments to protect its portfolio from
movements in securities' prices and interest rates. The Portfolio may use a
variety of currency hedging techniques, including forward currency contracts, to
manage exchange rate risk when investing directly in foreign markets. See
"Additional Risk Factors" on page 11. In addition, to the extent that the
Portfolio holds a larger cash position, it may not participate in market
declines to the same extent as if the Portfolio remained more fully invested in
common stocks.

FLEXIBLE INCOME PORTFOLIO IS DESIGNED FOR THOSE INVESTORS WHO PRIMARILY SEEK
CURRENT INCOME.

TYPES OF INVESTMENTS
In addition to the investment policies described above, Flexible Income
Portfolio may purchase securities on a when-issued, delayed delivery or forward
commitment basis. It may also use futures, options and other derivatives for
hedging purposes or for non-hedging purposes such as seeking to enhance return.
See "Additional Risk Factors" on page 11. When the portfolio manager is unable
to locate investment opportunities with favorable risk/reward characteristics,
the cash position of Flexible Income Portfolio may increase and the Portfolio
may

8 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

have substantial holdings of cash or cash equivalent short-term obligations. See
"General Portfolio Policies" on page 10.

THE FOLLOWING QUESTIONS ARE DESIGNED TO HELP YOU BETTER UNDERSTAND AN INVESTMENT
IN FLEXIBLE INCOME PORTFOLIO.

Q: HOW DO INTEREST RATES AFFECT THE VALUE OF MY INVESTMENT?

A: A fundamental risk associated with any fund that invests in fixed-income
securities (e.g., a bond fund) is the risk that the value of the securities it
holds will rise or fall as interest rates change. Generally, a fixed-income
security will increase in value when interest rates fall and decrease in value
when interest rates rise. Longer-term securities are generally more sensitive to
interest rate changes than shorter-term securities, but they generally offer
higher yields to compensate investors for the associated risks. High-yield bond
prices are generally less directly responsive to rate changes than investment
grade issues and may not always follow this pattern. A bond fund's
average-weighted effective maturity and its duration are measures of how the
portfolio may react to interest rate changes.

Q: WHAT IS MEANT BY THE PORTFOLIO'S "AVERAGE-WEIGHTED EFFECTIVE MATURITY"?

A: The stated maturity of a bond is the date when the issuer must repay the
bond's entire principal value to an investor, such as the Portfolio. Some types
of bonds, such as mortgage-backed securities, which are subject to prepayment
risk, and securities with call provisions, may also have an "effective maturity"
that is shorter than the stated date. With respect to GNMA securities and other
mortgage-backed securities, effective maturity is likely to be substantially
less than the stated maturities of the mortgages in the underlying pools. With
respect to obligations with call provisions, effective maturity is typically the
next call date on which the obligation reasonably may be expected to be called.
Securities without prepayment or call provisions generally have an effective
maturity equal to their stated maturity. Dollar-weighted effective maturity is
calculated by averaging the effective maturity of bonds held by a Portfolio with
each effective maturity "weighted" according to the percentage of net assets
that it represents.

Q: WHAT IS MEANT BY THE PORTFOLIO'S "DURATION"?

A: A bond's duration indicates the time it will take an investor to recoup his
or her investment. Unlike average maturity, duration reflects both principal and
interest payments. Generally, the higher the coupon rate on a bond, the lower
its duration will be. The duration of a bond fund is calculated by averaging the
duration of bonds held by the Portfolio with each duration "weighted" according
to the percentage of net assets that it represents. Because duration accounts
for interest payments, the Portfolio's duration is usually shorter than its
average maturity.

Q: HOW DOES THE PORTFOLIO MANAGE INTEREST RATE RISK?

A: The Portfolio may vary its average-weighted effective maturity to reflect
its portfolio manager's analysis of interest rate trends and other factors. The
Portfolio's average-weighted effective maturity will tend to be shorter when the
portfolio manager expects interest rates to rise and longer when the portfolio
manager expects interest rates to fall. The Portfolio may also use futures,
options and other derivatives to manage interest rate risk. See "Additional Risk
Factors" on page 11.

Q: WHAT IS MEANT BY "CREDIT QUALITY"?

A: Credit quality measures the likelihood that the issuer will meet its
obligations on a bond. One of the fundamental risks associated with all bond
funds is credit risk, which is the risk that an issuer will be unable to make
principal and interest payments when due. U.S. government securities are
generally considered to be the safest type of investment in terms of credit
risk. Municipal obligations generally rank between U.S. government securities
and corporate debt securities in terms of credit safety. Corporate debt
securities, particularly those rated below investment grade, present the highest
credit risk.

Q: HOW IS CREDIT QUALITY MEASURED?

A: Ratings published by nationally recognized rating agencies such as Standard
& Poor's Rating Services ("Standard & Poor's") and Moody's Investors Service,
Inc. ("Moody's") are widely accepted measures of credit risk. The lower a bond
issue is rated by an agency, the more credit risk it is considered to represent.
Lower rated bonds generally pay higher yields to compensate investors for the
associated risk. Please refer to Appendix B for a description of rating
categories.

Q: WHAT IS A HIGH-YIELD/HIGH-RISK SECURITY?

A: A high-yield security (also called a "junk" bond) is a debt security rated
below investment grade by major rating agencies (i.e., BB or lower by Standard &
Poor's or Ba or lower by Moody's) or an unrated bond of similar quality. It
presents greater risk of default (the failure to make timely interest and
principal payments) than higher quality bonds.

Q: WHAT RISKS DO HIGH-YIELD/HIGH-RISK SECURITIES PRESENT?

A: High-yield securities are often considered to be more speculative and
involve greater risk of default or price changes due to changes in economic and
industry conditions and the issuer's creditworthiness. Their market prices tend
to fluctuate more than higher quality securities as a result of changes in these
factors.

The default rate of lower quality debt securities is likely to be higher when
issuers have difficulty meeting projected goals or obtaining additional
financing.
JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 9
<PAGE>

This could occur during economic recessions or periods of high interest rates.
In addition, there may be a smaller market for lower quality securities than for
higher quality securities, making lower quality securities more difficult to
sell promptly at an acceptable price.

GENERAL PORTFOLIO POLICIES
In investing its assets, the Portfolios will follow the general policies listed
below. The percentage limitations included in these policies and elsewhere in
this Prospectus apply only at the time of purchase of the security. For example,
if a Portfolio exceeds a limit as a result of market fluctuations or the sale of
other securities, it will not be required to dispose of any securities.

CASH POSITION
When a Portfolio's manager believes that market conditions are not favorable for
profitable investing or when the portfolio manager is otherwise unable to locate
favorable investment opportunities, a Portfolio's investments may be hedged to a
greater degree and/or its cash or similar investments may increase. In other
words, the Portfolios do not always stay fully invested in stocks and bonds.
Cash or similar investments are a residual - they represent the assets that
remain after a portfolio manager has committed available assets to desirable
investment opportunities. Partly because portfolio managers act independently of
each other, the cash positions of the Portfolios may vary significantly. A
larger hedged position and/or larger cash position may serve as a means of
preserving capital in unfavorable market conditions.

Securities that the Portfolios may invest in as means of receiving a return on
idle cash include high-grade commercial paper, certificates of deposit,
repurchase agreements or other short-term debt obligations. The Portfolios may
also invest in money market funds (including funds managed by Janus Capital).
When a Portfolio is headed or its investments in cash or similar investments
increase, it may not participate in stock or bond market advances or declines to
the same extent that it would if the Portfolio was not hedged or remained more
fully invested in stocks or bonds.

DIVERSIFICATION
The Investment Company Act of 1940 (the "1940 Act") classifies investment
companies as either diversified or nondiversified. Both Portfolios qualify as
diversified funds under the 1940 Act and are subject to the following
diversification requirements:

- - As a fundamental policy, neither Portfolio may own more than 10% of the
outstanding voting shares of any issuer.

- - As a fundamental policy, with respect to 75% of the total assets of the
Portfolio, neither Portfolio will purchase a security of any issuer (other
than cash items and U.S. government securities, as defined in the 1940 Act) if
such purchase would cause the Portfolio's holdings of that issuer to amount to
more than 5% of the Portfolio's total assets.

- - Neither Portfolio will invest more than 25% of its total assets in a single
issuer (other than U.S. government securities).

INTERNAL REVENUE SERVICE (IRS) LIMITATIONS
In addition to the diversification requirements stated above, both Portfolios
intend to comply with the diversification requirements currently imposed by the
IRS on separate accounts of insurance companies as a condition of maintaining
the tax-deferred status of variable contracts. More specific information may be
contained in the participating insurance company's separate account prospectus.

INDUSTRY CONCENTRATION
As a fundamental policy, neither Portfolio will invest 25% or more of its total
assets in any particular industry (excluding U.S. government securities).

PORTFOLIO TURNOVER
Each Portfolio generally intends to purchase securities for long-term investment
rather than short-term gains. However, short-term transactions may result from
liquidity needs, securities having reached a price or yield objective, changes
in interest rates or the credit standing of an issuer, or by reason of economic
or other developments not foreseen at the time of the initial investment
decision. Changes are made in a Portfolio whenever the portfolio manager
believes such changes are desirable. Portfolio turnover rates are generally not
a factor in making buy and sell decisions.

10 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

BORROWING AND LENDING
Each Portfolio may borrow money and lend securities or other assets, as follows:

- - Each Portfolio may borrow money for temporary or emergency purposes in amounts
up to 25% of its total assets.

- - Each Portfolio may mortgage or pledge securities as collateral for borrowings
in amounts up to 15% of its net assets.

- - As a fundamental policy, each Portfolio may lend securities or other assets
if, as a result, no more than 25% of its total assets would be lent to other
parties.

Under the terms of an exemptive order received from the SEC, each Portfolio may
borrow money from or lend money to each other and other funds that permit such
transactions and for which Janus Capital serves as investment adviser. All such
borrowing and lending will be subject to the above percentage limits.

ADDITIONAL RISK FACTORS

FOREIGN SECURITIES
INVESTMENTS IN FOREIGN SECURITIES, INCLUDING THOSE OF FOREIGN GOVERNMENTS, MAY
INVOLVE GREATER RISKS THAN INVESTING IN COMPARABLE DOMESTIC SECURITIES.

Securities of some foreign companies and governments may be traded in the United
States, but many foreign securities are traded primarily in foreign markets. The
risks of foreign investing include:

- - POLITICAL AND ECONOMIC RISK. Foreign investments may be subject to heightened
political and economic risks, particularly in underdeveloped or developing
countries which may have relatively unstable governments and economies based
on only a few industries. In some countries, there is the risk that the
government may take over the assets or operations of a company or that the
government may impose taxes or limits on the removal of the Portfolio's assets
from that country. The Portfolios may invest in emerging market countries.
Emerging market countries involve greater risks such as immature economic
structures, national policies restricting investments by foreigners, and
different legal systems.

- - TRANSACTION COSTS. Transaction costs of buying and selling foreign
securities, including brokerage, tax and custody costs, are generally higher
than those involved in domestic transactions.

INVESTMENTS IN SMALLER COMPANIES
SMALLER OR NEWER COMPANIES MAY SUFFER MORE SIGNIFICANT LOSSES AS WELL AS REALIZE
MORE SUBSTANTIAL GROWTH THAN LARGER OR MORE ESTABLISHED ISSUERS.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 11
<PAGE>

The use of derivative instruments exposes each Portfolio to additional
investment risks and transaction costs. Risks inherent in the use of derivative
instruments include:

- - the risk that interest rates, securities prices and currency markets will not
move in the direction that a portfolio manager anticipates;

- - imperfect correlation between the price of derivative instruments and
movements in the prices of the securities, interest rates or currencies being
hedged;

- - the fact that skills needed to use these strategies are different from those
needed to select portfolio securities;

- - inability to close out certain hedged positions to avoid adverse tax
consequences;

Although the Portfolios' managers believe the use of derivative instruments will
benefit the Portfolio, a Portfolio's performance could be worse than if the
Portfolio had not used such instruments if the portfolio manager's judgment
proves incorrect.

When the Portfolio invests in a derivative instrument, it may be required to
segregate cash and other liquid assets or certain portfolio securities with its
custodian to "cover" the Portfolio's position. Assets segregated or set aside
generally may not be disposed of so long as the Portfolio maintains the
positions requiring segregation or cover. Segregating assets could diminish the
Portfolio's return due to the opportunity losses of foregoing other potential
investments with the segregated assets.

The market prices of high-yield/high-risk securities structured as zero coupon
or pay-in-kind securities are generally affected to a greater extent by interest
rate changes and tend to be more volatile than securities which pay interest
periodically. In addition, zero coupon, pay-in-kind and delayed interest bonds
often do not pay interest until maturity. However, a Portfolio must recognize
imputed interest income and pay dividends to shareholders even though it has
received no cash. In some instances, a Portfolio may have to sell securities to
have sufficient cash to pay the dividends.

Please refer to Appendix B for a description of bond rating categories.

12 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

other extraordinary corporate event, or differences in market supply of and
demand for the security. Investment in special situations may carry an
additional risk of loss in the event that the anticipated development does not
occur or does not attract the expected attention.

See Appendix A for risks associated with certain other investments.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 13
<PAGE>

MANAGEMENT OF THE PORTFOLIO

TRUSTEES
The Trustees oversee the business affairs of the Trust and are responsible for
major decisions relating to the Portfolio's investment objective and policies.
The Trustees delegate the day-to-day management of the Portfolio to the officers
of the Trust and meet at least quarterly to review the Portfolio's investment
policies, performance, expenses and other business affairs.

Participating insurance companies that purchase the Portfolio's Shares may
perform certain administrative services relating to the Portfolios and Janus
Capital or the Portfolios may pay those companies for such services.

INVESTMENT PERSONNEL
PORTFOLIO MANAGERS
HELEN YOUNG HAYES is Executive Vice President and portfolio manager of Worldwide
Growth Portfolio and co-manager of International Growth Portfolio which she has
managed or co-managed since inception. Ms. Hayes joined Janus Capital in 1987
and has managed or co-managed Janus Worldwide Fund and Janus Overseas Fund since
their inceptions. She holds a Bachelor of Arts in Economics from Yale University
and is a Chartered Financial Analyst.

RONALD V. SPEAKER is Executive Vice President and portfolio manager of Flexible
Income Portfolio, which he has managed or co-managed since its inception. He
previously served as co-manager of High-Yield Portfolio, from its inception to
May 1998. He managed Short-Term Bond Portfolio from its inception through April
1996. Mr. Speaker joined Janus Capital in 1986. He has managed or co-managed
Janus Flexible Income Fund since December 1991 and previously managed both Janus
Short-Term Bond Fund and Janus Federal Tax-Exempt Fund from inception through
December 1995. He previously managed or co-managed Janus High-Yield Fund from
its inception to February 1998. He holds a Bachelor of Arts in Finance from the
University of Colorado and is a Chartered Financial Analyst.

In January 1997, Mr. Speaker settled an SEC administrative action involving two
personal trades made by him in January of 1993. Without admitting or denying the
allegations, Mr. Speaker agreed to civil money penalty, disgorgement, and
interest payments totaling $37,199 and to a 90-day suspension which ended on
April 25, 1997.

PERSONAL INVESTING
Janus Capital does not permit portfolio managers to purchase and sell securities
for their own accounts, except under the limited exception in Janus Capital's
policy governing personal investing. Janus Capital's policy requires investment
and other personnel to conduct their personal investment activities in a manner
that Janus Capital believes is not detrimental to the Portfolio or Janus
Capital's other advisory clients. See the SAI for more detailed information.

14 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

following management fee schedule (expressed as an annual rate):

<TABLE>
<CAPTION>
AVERAGE DAILY
NET ASSETS ANNUAL RATE EXPENSE LIMIT
FEE SCHEDULE OF PORTFOLIO PERCENTAGE(%) PERCENTAGE(%)
B2
- ------------------------------------------------------------
<S> <C> <C> <C>
Worldwide Growth First $300 Million 0.75 N/A(1)
Portfolio Next $200 Million 0.70
Over $500 Million 0.65

Flexible Income First $300 Million .65 1.00(2)
Portfolio Over $300 Million .55
- -------------------------------------------------------------------------
</TABLE>

(1) Janus Capital has agreed to reduce Worldwide Growth Portfolio's advisory
fee to the extent that such fee exceeds the effective rate of the Janus
retail fund corresponding to such Portfolio. Janus Capital may terminate
this fee reduction at any time upon at least 90 days' notice to the
Trustees. The effective rate is the advisory fee calculated by the
corresponding retail fund as of the last day of each calendar quarter
(expressed as an annual rate). The effective rate of Janus Worldwide Fund
was .65% for the quarter ended March 31, 1998.

(2) Janus Capital may terminate or modify the expense limitation at anytime
upon at least 90 days' notice to the Trustees.

Differences in the actual management fees incurred by the Portfolios are due
primarily to variances in the asset sizes of the corresponding retail funds. As
asset size increases, the annual rate of the management fee declines in
accordance with the above schedule. In addition, the Shares of each Portfolio
incur expenses not assumed by Janus Capital, including transfer agent and
custodian fees and expenses, legal and auditing fees, printing and mailing costs
of sending reports and other information to existing shareholders, and
independent Trustees' fees and expenses. The fee schedule for the Worldwide
Growth Portfolio was effective July 1, 1997.

The management fee expressed as a percentage of average net assets paid by the
Worldwide Growth Portfolio during the most recent fiscal year was .66%.

PORTFOLIO TRANSACTIONS
Purchases and sales of securities on behalf of the Portfolios are executed by
broker-dealers selected by Janus Capital. Broker-dealers are selected on the
basis of their ability to obtain best price and execution for each Portfolio's
transactions and recognizing brokerage, research and other services provided to
the Portfolio and to Janus Capital. Janus Capital may consider sales of shares
of the Portfolios or other Janus funds by a broker-dealer or the recommendation
of a broker-dealer to its customers that they purchase a Portfolio's shares as a
factor in the selection of broker-dealers to execute portfolio transactions.
Janus Capital may also consider payments made by brokers effecting transactions
for a Portfolio i) to the Portfolio or ii) to other persons on behalf of the
Portfolio for services provided to the Portfolio for which it would be obligated
to pay. The Portfolios' Trustees have authorized Janus Capital to place
portfolio transactions on an agency basis with a broker-dealer affiliated with
Janus Capital. When transactions for the Portfolio are effected with that
broker-dealer, the commissions payable by the Portfolio are credited against
certain Portfolio operating expenses serving to reduce those expenses. The SAI
further explains the selection of broker-dealers.

OTHER SERVICE PROVIDERS

The following parties provide the Portfolios with administrative and other
services.

CUSTODIAN
State Street Bank and Trust Company
P.O. Box 0351
Boston, Massachusetts 02117-0351

TRANSFER AGENT
Janus Service Corporation
P.O. Box 173375
Denver, Colorado 80217-3375

Janus Service Corporation is a wholly-owned subsidiary of Janus Capital.

SHAREHOLDER MEETINGS AND VOTING RIGHTS
The Trust does not intend to hold annual shareholder meetings. However, special
meetings may be called for a specific class or Portfolio or for the Trust as a
whole for purposes such as electing or removing Trustees, terminating or
reorganizing the Trust, changing fundamental policies, or for any other purpose
requiring a shareholder vote under the 1940 Act. Separate votes are taken by
each class or Portfolio only if a matter affects or requires the vote of only
that class or Portfolio or the interest of a class or Portfolio in the matter
differs from the interest of other class or Portfolios of the Trust. As a
shareholder, you are entitled to one vote for each share that you own.

An insurance company issuing a variable contract invested in Shares of a
Portfolio will request voting instructions from variable contract holders. Under
current law, the insurance

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 15
<PAGE>

company must vote all Shares held by the separate account in proportion to the
voting instructions received.

CONFLICTS OF INTEREST
Each Portfolio's Shares are available only to variable annuity and variable life
separate accounts of insurance companies that are unaffiliated with Janus
Capital and to certain qualified retirement plans. Retirement Shares of the
Portfolios (offered through a separate prospectus) are available to certain
participant directed qualified plans. Although the Portfolios do not currently
anticipate any disadvantages to policy owners arising out of the fact that it
offers its shares to such entities, there is a possibility that a material
conflict may arise. The Trustees monitor events in order to identify any
anticipated disadvantages or material irreconcilable conflicts that may arise
and to determine what action, if any, should be taken in response. If a material
disadvantage or conflict occurs, the Trustees may require one or more insurance
company separate accounts or plans to withdraw its investment in one or more
Portfolios or substitute shares of another Portfolio. If this occurs, a
Portfolio may be forced to sell securities at disadvantageous prices. In
addition, the Trustees may refuse to sell shares of any Portfolio to any
separate account or may suspend or terminate the offering of a Portfolio's
shares if such action is required by law or regulatory authority or is in the
best interests of that Portfolio's shareholders. It is possible that a qualified
plan investing in the Retirement Shares of the Portfolios could lose its
qualified plan status under the Internal Revenue Code, which could have adverse
tax consequences on insurance company separate accounts investing in the Shares.
Janus Capital intends to monitor such qualified plans and the Portfolios may
discontinue sales to a qualified plan and require plan participants with
existing investments in the Retirement Shares to redeem those investments if a
plan loses (or in the opinion of Janus Capital is at risk of losing) its
qualified plan status.

THE VALUATION OF SHARES
The NAV of the Shares of a Portfolio is determined at the close of the regular
trading session of the New York Stock Exchange (the "NYSE") (normally 4:00 p.m.,
New York time) each day that the NYSE is open. NAV per Share is determined by
dividing the total value of the securities and other assets, less liabilities,
by the total number of Shares outstanding.

16 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

DISTRIBUTIONS AND TAXES

DISTRIBUTIONS
TO AVOID TAXATION OF THE PORTFOLIOS, THE INTERNAL REVENUE CODE REQUIRES EACH
PORTFOLIO TO DISTRIBUTE NET INCOME AND ANY NET GAINS REALIZED ON ITS INVESTMENTS
ANNUALLY. ORDINARY INCOME FROM DIVIDENDS AND INTEREST AND ANY NET REALIZED
SHORT-TERM GAINS ARE PAID TO SHAREHOLDERS AS ORDINARY INCOME DIVIDENDS. NET
REALIZED LONG-TERM GAINS, IF ANY, ARE PAID TO SHAREHOLDERS AS CAPITAL GAINS
DISTRIBUTIONS. EACH CLASS OF EACH PORTFOLIO MAKES SEMIANNUAL DISTRIBUTIONS IN
JUNE AND DECEMBER OF SUBSTANTIALLY ALL OF ITS INVESTMENT INCOME AND AN ANNUAL
DISTRIBUTION IN JUNE OF ITS NET REALIZED GAINS, IF ANY. ALL DIVIDENDS AND
CAPITAL GAINS DISTRIBUTIONS FROM THE SHARES OF A PORTFOLIO WILL BE AUTOMATICALLY
REINVESTED INTO ADDITIONAL SHARES OF THAT PORTFOLIO.

HOW DISTRIBUTIONS AFFECT NAV
Distributions are paid to shareholders as of the record date of the distribution
of a Portfolio, regardless of how long the shares have been held. Undistributed
income and realized gains are included in the daily NAV of a Portfolio's Shares.
The Share price of the Portfolio drops by the amount of the distribution, net of
any subsequent market fluctuations. For example, assume that on December 31, the
Shares of Worldwide Growth Portfolio declared a dividend in the amount of $0.25
per share. If the price of Worldwide Growth Portfolio's Shares was $10.00 on
December 30, the Share price on December 31 would be $9.75, barring market
fluctuations.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 17
<PAGE>

SHAREHOLDER'S GUIDE

PURCHASES
Purchases of Shares may be made only by the separate accounts of insurance
companies for the purpose of funding variable insurance contracts or by
qualified plans. Refer to the prospectus of the appropriate insurance company's
separate account or your plan documents for information on how to invest in the
Shares of each Portfolio.

Each Portfolio reserves the right to reject any specific purchase order.
Purchase orders may be refused if, in Janus Capital's opinion, they are of a
size that would disrupt the management of a Portfolio. Either Portfolio may
discontinue sales of its shares if management believes that a substantial
further increase may adversely affect that Portfolio's ability to achieve its
investment objective. In such event, however, it is anticipated that existing
policy owners and plan participants invested in that Portfolio would be
permitted to continue to authorize investment in such Portfolio and to reinvest
any dividends or capital gains distributions.

Shares of either Portfolio may be redeemed on any business day. Redemptions are
processed at the NAV next calculated after receipt and acceptance of the
redemption order by the Portfolio. Redemption proceeds will normally be wired to
the participating insurance company the business day following receipt of the
redemption order, but in no event later than seven days after receipt of such
order.

18 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

APPENDIX A

CONVERTIBLE SECURITIES are preferred stocks or bonds that pay a fixed dividend
or interest payment and are convertible into common stock at a specified price
or conversion ratio.

MORTGAGE- AND ASSET-BACKED SECURITIES are shares in a pool of mortgages or other
debt. These securities are generally pass-through securities, which means that
principal and interest payments on the underlying securities (less servicing
fees) are passed through to shareholders on a pro rata basis. These securities
involve prepayment risk, which is the risk that the underlying mortgages or
other debt may be refinanced or paid off prior to their maturities during
periods of declining interest rates. In that case, a portfolio manager may have
to reinvest the proceeds from the securities at a lower rate. Potential market
gains on a security subject to prepayment risk may be more limited than
potential market gains on a comparable security that is not subject to
prepayment risk.

PREFERRED STOCK is a class of stock that generally pays dividends at a specified
rate and has preference over common stock in the payment of dividends and
liquidation. Preferred stock generally does not carry voting rights. Repurchase
agreements involve the purchase of a security by a Portfolio and a simultaneous
agreement by the seller (generally a bank or dealer) to repurchase the security
from the Portfolio at a specified date or upon demand. This technique offers a
method of earning income on idle cash. These securities involve the risk that
the seller will fail to repurchase the security, as agreed. In that case, a
Portfolio will bear the risk of market value fluctuations until the security can
be sold and may encounter delays and incur costs in liquidating the security.

RULE 144A SECURITIES are securities that are not registered for sale to the
general public under the Securities Act of 1933, but that may be resold to
certain institutional investors.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 19
<PAGE>

STANDBY COMMITMENTS are obligations purchased by the Portfolio from a dealer
that give the Portfolio the option to sell a security to the dealer at a
specified price.

WHEN-ISSUED, DELAYED DELIVERY AND FORWARD TRANSACTIONS generally involve the
purchase of a security with payment and delivery at some time in the
future - i.e., beyond normal settlement. The Portfolios do not earn interest on
such securities until settlement and bears the risk of market value fluctuations
between the purchase and settlement dates. New issues of stocks and bonds,
private placements and U.S. government securities may be sold in this manner.

II. FUTURES, OPTIONS
AND OTHER DERIVATIVES
FORWARD CONTRACTS are contracts to purchase or sell a specified amount of a
financial instrument for an agreed upon price at a specified time. Forward
contracts are not currently exchange traded and are typically negotiated on an
individual basis. The Portfolios may enter into forward currency contracts to
hedge against declines in the value of non-dollar denominated securities or to
reduce the impact of currency appreciation on purchases of non-dollar
denominated securities. The Portfolios may also enter into forward contracts to
purchase or sell securities or other financial indices.

20 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

INVERSE FLOATERS are debt instruments whose interest rate bears an inverse
relationship to the interest rate on another instrument or index. For example,
upon reset the interest rate payable on a security may go down when the
underlying index has risen. Certain inverse floaters may have an interest rate
reset mechanism that multiplies the effects of change in the underlying index.
Such mechanism may increase the volatility of the security's market value.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 21
<PAGE>

APPENDIX B

EXPLANATION OF RATING CATEGORIES

The following is a description of credit ratings issued by two of the major
credit ratings agencies. Credit ratings evaluate only the safety of principal
and interest payments, not the market value risk of lower quality securities.
Credit rating agencies may fail to change credit ratings to reflect subsequent
events on a timely basis. Although the adviser considers security ratings when
making investment decisions, it also performs its own investment analysis and
does not rely solely on the ratings assigned by credit agencies.

STANDARD & POOR'S RATINGS SERVICES

MOODY'S INVESTORS SERVICE, INC.

<TABLE>
<S> <C>
INVESTMENT GRADE
Aaa Highest quality, smallest degree of
investment risk.
Aa High quality; together with Aaa bonds,
they compose the high-grade bond group.
A Upper-medium grade obligations; many
favorable investment attributes.
Baa Medium-grade obligations; neither highly
protected nor poorly secured. Interest
and principal appear adequate for the
present but certain protective elements
may be lacking or may be unreliable over
any great length of time.
NON-INVESTMENT GRADE
Ba More uncertain, with speculative
elements. Protection of interest and
principal payments not well safeguarded
during good and bad times.
B Lack characteristics of desirable
investment; potentially low assurance of
timely interest and principal payments
or maintenance of other contract terms
over time.
Caa Poor standing, may be in default;
elements of danger with respect to
principal or interest payments.
Ca Speculative in a high degree; could be
in default or have other marked
shortcomings.
C Lowest-rated; extremely poor prospects
of ever attaining investment standing.
- --------------------------------------------------------------
</TABLE>

<TABLE>
<CAPTION>
BONDS - S&P RATING FLEXIBLE INCOME PORTFOLIO
<S> <C>
AAA 21%
AA 0%
A 15%
BBB 12%
BB 11%
B 27%
CCC 1%
CC 0%
C 0%
Preferred Stock 2%
Cash and Options 11%
- -----------------------------------------------------------------
TOTAL 100%
- -----------------------------------------------------------------
</TABLE>

No other Portfolio held 5% or more of its assets in bonds rated below investment
grade for the fiscal year ended December 31, 1997.

22 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

This page intentionally left blank.
<PAGE>
JANUS ASPEN SERIES
PROSPECTUS
Worldwide Growth Portfolio
Flexible Income Portfolio

[JANUS LOGO]

P.O. Box 173375 o Denver, CO 80217-3375 o 1-800-525-1068
(5/98)
<PAGE>

JANUS ASPEN SERIES

Prospectus

MAY 1, 1998

This prospectus describes five mutual funds with a variety of investment
objectives, including growth of capital, current income and a combination of
growth and income (the "Portfolios"). Each Portfolio is a series of Janus Aspen
Series (the "Trust") and currently offers two classes of shares. The
Institutional Shares are sold under the name "Janus Aspen Series." The Trust is
registered with the Securities and Exchange Commission ("SEC") as an open-end
management investment company. The Institutional Shares of each Portfolio
(collectively, the "Shares") are offered by this prospectus in connection with
investment in and payments under variable annuity contracts and variable life
insurance contracts (collectively "variable insurance contracts"), as well as
certain qualified retirement plans. Janus Capital Corporation ("Janus Capital")
serves as investment adviser to each Portfolio. Janus Capital has been in the
investment advisory business for over 27 years and currently manages
approximately $80 billion in assets.

THESE SECURITIES HAVE NOT BEEN APPROVED BY THE SEC NOR HAS THE SEC PASSED ON THE
ACCURACY OR ADEQUACY OF THIS PROSPECTUS. ANY REPRESENTATION TO THE CONTRARY IS A
CRIMINAL OFFENSE.

THIS PROSPECTUS DOES NOT CONSTITUTE AN OFFER TO SELL SECURITIES IN ANY STATE OR
OTHER JURISDICTION TO ANY PERSON TO WHOM IT IS UNLAWFUL TO MAKE SUCH AN OFFER IN
SUCH STATE OR OTHER JURISDICTION.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

CONTENTS

<TABLE>
<S> <C>
PORTFOLIOS AT A GLANCE
Brief description of the Portfolios......................... 2
EXPENSE INFORMATION
Each Portfolio's annual operating expenses.................. 3
Financial Highlights - a summary of financial data.......... 4
PERFORMANCE TERMS
An explanation of performance terms......................... 7
THE PORTFOLIOS IN DETAIL
Investment Objectives and Policies.......................... 8
General Portfolio Policies.................................. 10
Additional Risk Factors..................................... 11
MANAGEMENT OF THE PORTFOLIOS
Investment Adviser and Investment Personnel................. 14
Personal Investing.......................................... 15
Management Expenses......................................... 15
Portfolio Transactions...................................... 15
Other Service Providers..................................... 15
Other Information........................................... 15
DISTRIBUTIONS AND TAXES
Distributions............................................... 17
Taxes....................................................... 17
SHAREHOLDER'S GUIDE
Purchases................................................... 18
Redemptions................................................. 18
Shareholder Communications.................................. 18
APPENDIX A
Glossary of Investment Terms................................ 19
</TABLE>

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 1
<PAGE>

PORTFOLIOS AT A GLANCE

INTERNATIONAL GROWTH PORTFOLIO
Focus: A diversified portfolio that seeks long-term growth of capital by
investing primarily in common stocks of foreign issuers.
Inception: May 1994
Managers:Laurence J. Chang
Helen Young Hayes

2 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

EXPENSE INFORMATION

SHAREHOLDER TRANSACTION EXPENSES (applicable to each Portfolio)

ANNUAL OPERATING EXPENSES (after fee reductions)(1)
(expressed as a percentage of average net assets)

<TABLE>
<CAPTION>
- -----------------------------------------------------------------------------------------------------------------
MANAGEMENT OTHER TOTAL OPERATING
FEE EXPENSES EXPENSES
- -----------------------------------------------------------------------------------------------------------------
<S> <C> <C> <C>
Growth Portfolio 0.65% 0.05% 0.70%
Aggressive Growth Portfolio 0.73% 0.03% 0.76%
International Growth Portfolio 0.67% 0.29% 0.96%
Worldwide Growth Portfolio 0.66% 0.08% 0.74%
Balanced Portfolio 0.76% 0.07% 0.83%
----------------------------------------------------------------------------------------------------------------
</TABLE>

(1) Management fees for Growth, Aggressive Growth, International Growth,
Worldwide Growth and Balanced Portfolios reflect a reduced fee schedule
effective July 1, 1997. The management fee for each Portfolio reflects the
new rate applied to net assets as of December 31, 1997. Other expenses are
based on the gross expenses of the Shares before expense offset arrangements
for the fiscal year ended December 31, 1997. The information for each
Portfolio is net of fee reductions from Janus Capital. Fee reductions for
Growth, Aggressive Growth, International Growth, Worldwide Growth and
Balanced Portfolios reduce the management fee to the level of the
corresponding Janus retail fund. Without such reductions, the Management
Fee, Other Expenses and Total Operating Expenses for the Shares would have
been 0.74%, 0.04% and 0.78% for Growth Portfolio; 0.74%, 0.04%, and 0.78%
for Aggressive Growth Portfolio; 0.79%, 0.29%, and 1.08% for International
Growth Portfolio; 0.72%, 0.09%, and 0.81% for Worldwide Growth Portfolio,
and 0.77%, 0.06%, and 0.83% for Balanced Portfolio, respectively. Janus
Capital may modify or terminate the fee reductions at any time upon at least
90 days' notice to the Trustees.

EXAMPLE

<TABLE>
<CAPTION>
- ---------------------------------------------------------------------------------------------------------------
1 YEAR 3 YEARS 5 YEARS 10 YEARS
- ---------------------------------------------------------------------------------------------------------------
<S> <C> <C> <C> <C>
Growth Portfolio $ 7 $22 $39 $ 87
Aggressive Growth Portfolio $ 8 $24 $42 $ 94
International Growth Portfolio $10 $31 $53 $118
Worldwide Growth Portfolio $ 8 $24 $41 $ 92
Balanced Portfolio $ 8 $26 $46 $103
--------------------------------------------------------------------------------------------------------------
</TABLE>

THE EXAMPLE SHOULD NOT BE CONSIDERED A REPRESENTATION OF PAST OR FUTURE RETURNS
OR EXPENSES WHICH MAY BE MORE OR LESS THAN THOSE SHOWN.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 3
<PAGE>

FINANCIAL HIGHLIGHTS

Unless otherwise stated, the information below is for fiscal periods ending on
December 31st of each year. The accounting firm of Price Waterhouse LLP has
audited the Portfolios' financial statements since their inception. Their report
is included in the Portfolios' Annual Report, which is incorporated by reference
into the SAI. A DETAILED EXPLANATION OF THE FINANCIAL HIGHLIGHTS CAN BE FOUND ON
PAGE 6.
<TABLE>
<CAPTION>
GROWTH PORTFOLIO
INSTITUTIONAL SHARES 1997 1996 1995 1994 1993(1)
- ---------------------------------------------------------------------------------------------------------
<C> <S> <C> <C> <C> <C> <C>
1. Net asset value, beginning of period $15.51 $13.45 $10.57 $10.32 $10.00
- ---------------------------------------------------------------------------------------------------------
INCOME FROM INVESTMENT OPERATIONS:
2. Net investment income .15 .17 .28 .09 .03
3. Net gains or (losses) on securities
(both realized and unrealized) 3.34 2.29 2.90 .20 .32
- ---------------------------------------------------------------------------------------------------------
4. Total from investment operations 3.49 2.46 3.18 .29 .35
- ---------------------------------------------------------------------------------------------------------
LESS DISTRIBUTIONS:
5. Dividends (from net investment income) (.15) (.17) (.30) (.04) (.03)
6. Tax return of capital -- -- -- -- --
7. Distributions (from capital gains) (.37) (.23) -- -- --
- ---------------------------------------------------------------------------------------------------------
8. Total distributions (.52) (.40) (.30) (.04) (.03)
- ---------------------------------------------------------------------------------------------------------
9. Net asset value, end of period $18.48 $15.51 $13.45 $10.57 $10.32
- ---------------------------------------------------------------------------------------------------------
10. Total return* 22.75% 18.45% 30.17% 2.76% 3.50%
- ---------------------------------------------------------------------------------------------------------
11. Net assets, end of period (in
thousands) $608,281 $325,789 $126,911 $43,549 $7,482
12. Average net assets for the period (in
thousands) $477,914 $216,125 $77,344 $26,464 $3,191
13. Ratio of gross expenses to average net
assets** 0.70%(8) 0.69%(7) 0.78%(6) N/A N/A
14. Ratio of net expenses to average net
assets** 0.69% 0.69% 0.76% 0.88%(3)(5) 0.25%(4)
15. Ratio of net investment income to
average net assets** 0.91% 1.39% 1.24% 1.45% 2.54%
16. Portfolio turnover rate** 122% 87% 185% 169% 162%
17. Average commission rate $0.0500 $0.0466 N/A N/A N/A
- ---------------------------------------------------------------------------------------------------------

<CAPTION>
AGGRESSIVE GROWTH PORTFOLIO
1997 1996 1995 1994 1993(1)

<C> <C> <C> <C> <C> <C>
1. $18.24 $17.08 $13.62 $11.80 $10.00
- ---------------------------------------------------------------------

2. -- -- .24 .11 .01
3.
2.31 1.36 3.47 1.82 1.80
- ---------------------------------------------------------------------
4. 2.31 1.36 3.71 1.93 1.81
- ---------------------------------------------------------------------

5. -- -- (.25) (.11) (.01)
6. -- (.01) -- -- --
7. -- (.19) -- -- --
- ---------------------------------------------------------------------
8. -- (.20) (.25) (.11) (.01)
- ---------------------------------------------------------------------
9. $20.55 $18.24 $17.08 $13.62 $11.80
- ---------------------------------------------------------------------
10. 12.66% 7.95% 27.48% 16.33% 18.05%
- ---------------------------------------------------------------------
11.
$508,198 $383,693 $185,911 $41,289 $1,985
12.
$418,464 $290,629 $107,582 $14,152 $1,091
13.
0.76%(8) 0.76%(7) 0.86%(6) N/A N/A
14.
0.76% 0.76% 0.84% 1.05%(3)(5) 0.25%(4)
15.
(0.10%) (0.27%) 0.58% 2.18% 0.34%
16. 130% 88% 155% 259% 31%
17. $0.0367 $0.0347 N/A N/A N/A
- ---------------------------------------------------------------------
</TABLE>
<TABLE>
<CAPTION>
INTERNATIONAL GROWTH PORTFOLIO
INSTITUTIONAL SHARES 1997 1996 1995 1994(2)
- ------------------------------------------------------------------------------------------------------
<C> <S> <C> <C> <C> <C>
1. Net asset value, beginning of period $15.72 $11.95 $9.72 $10.00
- ------------------------------------------------------------------------------------------------------
INCOME FROM INVESTMENT OPERATIONS:
2. Net investment income .11 .05 .09 (.09)
3. Net gains or (losses) on securities (both
realized and unrealized) 2.80 4.06 2.16 (.19)
- ------------------------------------------------------------------------------------------------------
4. Total from investment operations 2.91 4.11 2.25 (.28)
- ------------------------------------------------------------------------------------------------------
LESS DISTRIBUTIONS:
5. Dividends (from net investment income) (.11) (.11) (.02) --
6. Dividends (in excess of net investment income) -- -- -- --
7. Tax return of capital -- -- -- --
8. Distributions (from capital gains) (.01) (.23) -- --
9. Distributions (in excess of realized gains) (.03) -- -- --
- ------------------------------------------------------------------------------------------------------
10. Total distributions (.15) (.34) (.02) --
- ------------------------------------------------------------------------------------------------------
11. Net asset value, end of period $18.48 $15.72 $11.95 $9.72
- ------------------------------------------------------------------------------------------------------
12. Total return* 18.51% 34.71% 23.15% (2.80%)
- ------------------------------------------------------------------------------------------------------
13. Net assets, end of period (in thousands) $161,091 $27,192 $1,608 $1,353
14. Average net assets for the period (in
thousands) $96,164 $7,437 $1,792 $1,421
15. Ratio of gross expenses to average net assets** 0.96%(8) 1.26%(7) 2.69%(6) N/A
16. Ratio of net expenses to average net assets** 0.96% 1.25% 2.50% 2.50%(5)
17. Ratio of net investment income to average net
assets** 0.70% 0.62% (0.80%) (1.30%)
18. Portfolio turnover rate** 86% 65% 211% 275%
19. Average commission rate $0.0241 $0.0305 N/A N/A
- ------------------------------------------------------------------------------------------------------

<CAPTION>
WORLDWIDE GROWTH PORTFOLIO
1997 1996 1995 1994 1993(1)
- ------------------------------------------------------------------------------------------------------
<C> <C> <C> <C> <C> <C>
1. $19.44 $15.31 $12.07 $11.89 $10.00
- ------------------------------------------------------------------------------------------------------

2. .16 .16 .11 .04 .02
3.
4.14 4.27 3.19 .14 1.89
- ------------------------------------------------------------------------------------------------------
4. 4.30 4.43 3.30 .18 1.91
- ------------------------------------------------------------------------------------------------------

5. (.17) (.17) (.06) -- (.01)
6. (.02) -- -- -- --
7. -- -- -- -- --
8. (.16) (.13) -- -- (.01)
9. -- -- -- -- --
- ------------------------------------------------------------------------------------------------------
10. (.35) (.30) (.06) -- (.02)
- ------------------------------------------------------------------------------------------------------
11. $23.39 $19.44 $15.31 $12.07 $11.89
- ------------------------------------------------------------------------------------------------------
12. 22.15% 29.04% 27.37% 1.53% 19.10%
- ------------------------------------------------------------------------------------------------------
13. $1,576,548 $582,603 $108,563 $37,728 $4,856
14.
$1,148,951 $304,111 $59,440 $22,896 $2,200
15. 0.74%(8) 0.80%(7) 0.90%(6) N/A N/A
16. 0.74% 0.80% 0.87% 1.18%(3)(5) 0.25%(4)
17.
0.67% 0.83% 0.95% 0.50% 0.84%
18. 80% 62% 113% 217% 57%
19. $0.0337 $0.0345 N/A N/A N/A
- ------------------------------------------------------------------------------------------------------
</TABLE>

* Total return not annualized for periods of less than one year.
** Annualized for periods of less than one full year.
(1) September 13, 1993 (inception) to December 31, 1993.
(2) May 2, 1994 (inception) to December 31, 1994.
(3) Commissions payable by the Portfolio for transactions effected by a
broker-dealer affiliated with Janus Capital were credited against the
Portfolio's operating expenses. The effect of such directed brokerage
arrangement was de minimis.
(4) The ratio was 2.16%, 5.79% and 2.71%, respectively, for Growth, Aggressive
Growth and Worldwide Growth Portfolios, before waiver of certain fees,
and/or voluntary reduction of adviser's fees to the effective rate of the
corresponding Janus retail fund.
(5) The ratio was 1.23%, 1.14%, 4.67% and 1.49%, respectively, for Growth,
Aggressive Growth, International Growth and Worldwide Growth Portfolios,
before waiver of certain fees, and/or voluntary reduction of adviser's fees
to the effective rate of the corresponding Janus retail fund.
(6) The ratio was 0.98%, 0.93%, 3.57% and 1.09%, respectively, for Growth,
Aggressive Growth, International Growth and Worldwide Growth Portfolios,
before waiver of certain fees, and/or voluntary reduction of adviser's fees
to the effective rate of the corresponding Janus retail fund.
(7) The ratio was 0.83%, 0.83%, 2.21% and 0.91%, respectively, for Growth,
Aggressive Growth, International Growth and Worldwide Growth Portfolios,
before waiver of certain fees, and/or voluntary reduction of adviser's fees
to the effective rate of the corresponding Janus retail fund.
(8) The ratio was 0.78%, 0.78%, 1.08% and 0.81%, respectively, for Growth,
Aggressive Growth, International Growth and Worldwide Growth Portfolios,
before voluntary reduction of adviser's fees to the effective rate of the
corresponding Janus retail fund.

4 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

<TABLE>
<CAPTION>
BALANCED PORTFOLIO
INSTITUTIONAL SHARES 1997 1996 1995 1994 1993(1)
- ----------------------------------------------------------------------------------------------------------------------------------
<C> <S> <C> <C> <C> <C> <C>
1. Net asset value, beginning of period $14.77 $13.03 $10.63 $10.64 $10.00
- ----------------------------------------------------------------------------------------------------------------------------------
INCOME FROM INVESTMENT OPERATIONS:
2. Net investment income .34 .32 .17 .15 .08
3. Net gains or (losses) on securities (both realized and
unrealized) 2.89 1.81 2.45 (.06) .64
- ----------------------------------------------------------------------------------------------------------------------------------
4. Total from investment operations 3.23 2.13 2.62 .09 .72
- ----------------------------------------------------------------------------------------------------------------------------------
LESS DISTRIBUTIONS:
5. Dividends (from net investment income) (.35) (.30) (.22) (.10) (.08)
6. Tax return of capital distributions -- -- -- -- --
7. Distributions (from capital gains) (.18) (.09) -- -- --
- ----------------------------------------------------------------------------------------------------------------------------------
8. Total distributions (.53) (.39) (.22) (.10) (.08)
- ----------------------------------------------------------------------------------------------------------------------------------
9. Net asset value, end of period $17.47 $14.77 $13.03 $10.63 $10.64
- ----------------------------------------------------------------------------------------------------------------------------------
10. Total return* 22.10% 16.18% 24.79% 0.84% 7.20%
- ----------------------------------------------------------------------------------------------------------------------------------
11. Net assets, end of period (in thousands) $362,409 $85,480 $14,021 $3,153 $537
12. Average net assets for the period (in thousands) $176,432 $43,414 $5,739 $2,336 $521
13. Ratio of gross expenses to average net assets** 0.83%(7) 0.94%(6) 1.37%(5) N/A N/A
14. Ratio of net expenses to average net assets** 0.82% 0.92% 1.30% 1.57%(2)(4) 0.25%(3)
15. Ratio of net investment income to average net assets** 2.87% 2.92% 2.41% 1.90% 2.69%
16. Portfolio turnover rate** 139% 103% 149% 158% 126%
17. Average commission rate $0.0456 $0.0426 N/A N/A N/A
- ----------------------------------------------------------------------------------------------------------------------------------
</TABLE>

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 5
<PAGE>

UNDERSTANDING THE
FINANCIAL HIGHLIGHTS

RATIO OF NET INVESTMENT INCOME TO AVERAGE NET ASSETS is a Portfolio's net
investment income divided by its average net assets for the stated period.

AVERAGE COMMISSION RATE is the total of a Portfolio's agency commission paid on
equity securities trades divided by the number of shares purchased and sold.

6 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

PERFORMANCE TERMS

This section will help you understand various terms that are commonly used to
describe a Portfolio's performance. You may see references to these terms in our
newsletters or advertisements (or those published by participating insurance
companies) and in media articles. Newsletters and advertisements may include
comparisons of a Portfolio's performance to the performance of other mutual
funds, mutual fund averages or recognized stock market indices. Growth
Portfolio, Aggressive Growth Portfolio, International Growth Portfolio,
Worldwide Growth Portfolio and Balanced Portfolio generally measure performance
in terms of total return.

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 7
<PAGE>

THE PORTFOLIOS IN DETAIL

This section takes a closer look at the Portfolios' investment objectives,
policies and the securities in which they invest. Please carefully review the
"Additional Risk Factors" section of this Prospectus for a more detailed
discussion of the risks associated with certain investment techniques. Appendix
A contains a more detailed discussion of investment terms used throughout this
Prospectus. You should carefully consider your investment goals, time horizon
and risk tolerance before choosing a Portfolio.

Each Portfolio has an investment objective and policies that are similar to
those of a Janus retail fund, as illustrated in the chart below. Although it is
anticipated that each Portfolio and its corresponding retail fund will hold
similar securities, differences in asset size and cash flow needs as well as the
relative weightings of securities selections may result in differences in
investment performance. Expenses of each Portfolio and its corresponding retail
fund are expected to differ. The variable contract owner will also bear various
insurance-related costs at the insurance company level. You should review the
accompanying separate account prospectus for a summary of contract fees and
expenses.

EACH OF THE PORTFOLIOS HAS A SIMILAR INVESTMENT
OBJECTIVE AND SIMILAR INVESTMENT POLICIES TO AN EXISTING JANUS RETAIL FUND.

Growth Portfolio....................................................Janus Fund
Aggressive Growth Portfolio..............................Janus Enterprise Fund
International Growth Portfolio.............................Janus Overseas Fund
Worldwide Growth Portfolio................................Janus Worldwide Fund
Balanced Portfolio.........................................Janus Balanced Fund

GROWTH PORTFOLIO, AGGRESSIVE GROWTH PORTFOLIO, INTERNATIONAL GROWTH PORTFOLIO
AND WORLDWIDE GROWTH PORTFOLIO ARE DESIGNED FOR LONG-TERM INVESTORS WHO SEEK
GROWTH OF CAPITAL ONLY AND WHO CAN TOLERATE THE GREATER RISKS ASSOCIATED WITH
COMMON STOCK INVESTMENTS.

AGGRESSIVE GROWTH PORTFOLIO
The investment objective of this Portfolio is long-term growth of capital. It is
a nondiversified portfolio that pursues its investment objective by normally
investing at least 50% of its equity assets in securities issued by medium-sized
companies. Medium-sized companies are those whose market capitalizations fall
within the range of companies in the S&P MidCap 400 Index (the "MidCap Index").
Companies whose capitalization falls outside this range after the Portfolio's
initial purchase continue to be considered medium-sized companies for the
purpose of this policy. As of December 30, 1997, the MidCap Index included
companies with capitalizations between approximately $213 million and $13.7
billion. The range of the MidCap Index is expected to change on a regular basis.
Subject to the above policy, the Portfolio may also invest in smaller or larger
issuers.

INTERNATIONAL GROWTH PORTFOLIO
The investment objective of this Portfolio is long-term growth of capital. It is
a diversified portfolio that pursues its objective primarily through investments
in common stocks of issuers located outside the United States. The Portfolio has
the flexibility to invest on a worldwide basis in companies and other
organizations of any size, regardless of country of organization or place of
principal business activity. The Portfolio normally invests at least 65% of its
total assets in securities of issuers from at least five different countries,
excluding the United States. Although the Portfolio intends to invest
substantially all of its assets in issuers located outside the United States, it
may at times invest in U.S. issuers, and it may at times invest all of its
assets in fewer than five countries or even a single country.

TYPES OF INVESTMENTS
Each of these Portfolios invests primarily in common stocks of foreign and
domestic companies. However, the percentage of

8 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

each Portfolio's assets invested in common stocks will vary and each Portfolio
may at times hold substantial positions in cash equivalents or interest bearing
securities. See "General Portfolio Policies" on page 10. Each Portfolio may
invest to a lesser degree in other types of securities including preferred
stocks, warrants, convertible securities and debt securities when its portfolio
manager perceives an opportunity for capital growth from such securities or to
receive a return on idle cash. Some securities that the Portfolios purchase may
be on a when-issued, delayed delivery or forward commitment basis. The
Portfolios may invest up to 25% of their assets in mortgage- and asset-backed
securities, up to 10% of their assets in zero coupon, pay-in-kind and step
coupon securities, and without limit in indexed/structured securities. No Growth
Portfolio will invest 35% or more of its assets in high-yield/high-risk
securities.

Although International Growth Portfolio and Worldwide Growth Portfolio are
committed to foreign investing, Growth Portfolio and Aggressive Growth Portfolio
may also invest without limit in foreign equity and debt securities. The
Portfolios may invest directly in foreign securities denominated in a foreign
currency and not publicly traded in the United States. Other ways of investing
in foreign securities include depositary receipts or shares, and passive foreign
investment companies ("PFICs"). These Portfolios may use futures, options and
other derivatives for hedging purposes or for non-hedging purposes such as
seeking to enhance return. See "Additional Risk Factors" on page 11 for a
discussion of the risks associated with foreign investing and derivatives.

THE FOLLOWING QUESTIONS ARE DESIGNED TO HELP YOU BETTER UNDERSTAND AN INVESTMENT
IN THE GROWTH PORTFOLIOS.

Q: HOW ARE COMMON STOCKS SELECTED?

Q: ARE THE SAME CRITERIA USED TO SELECT FOREIGN SECURITIES?

Q: WHAT IS THE MAIN RISK OF INVESTING IN A GROWTH PORTFOLIO?

Q: WHAT IS MEANT BY "MARKET CAPITALIZATION"?

A: Market capitalization is the most commonly used measure of the size and
value of a company. It is computed by multiplying the current market price
of a share of the company's stock by the total number of its shares outstanding.
As noted previously, market capitalization is an important investment criteria
for Aggressive Growth Portfolio which may invest in small to medium sized
companies to a greater degree. Although Growth Portfolio, International Growth
Portfolio and Worldwide Growth Portfolio do not emphasize companies of any
particular size, Portfolios with a larger asset base are more likely to invest
in larger, more-established issuers.

Q: HOW DOES A DIVERSIFIED PORTFOLIO DIFFER FROM A NONDIVERSIFIED PORTFOLIO?

Q: HOW DO THESE PORTFOLIOS TRY TO REDUCE RISK?

JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998 9
<PAGE>

investing directly in foreign markets. See "Additional Risk Factors" on page 11.
In addition, to the extent that a Portfolio holds a larger cash position, it may
not participate in market declines to the same extent as if the Portfolio
remained more fully invested in common stocks.

BALANCED PORTFOLIO IS DESIGNED FOR INVESTORS WHO PRIMARILY SEEK GROWTH OF
CAPITAL WITH A DEGREE OF EMPHASIS ON INCOME. IT IS NOT DESIGNED FOR INVESTORS
WHO DESIRE A CONSISTENT LEVEL OF INCOME.

BALANCED PORTFOLIO
The investment objective of this Portfolio is long-term capital growth,
consistent with preservation of capital and balanced by current income. It is a
diversified Portfolio that, under normal circumstances, pursues its objective by
investing 40-60% of its assets in securities selected primarily for their growth
potential and 40-60% of its assets in securities selected primarily for their
income potential. This Portfolio normally invests at least 25% of its assets in
fixed-income senior securities, which include debt securities and preferred
stocks.

TYPES OF INVESTMENTS
Balanced Portfolio may invest in a combination of common stocks, preferred
stocks, convertible securities, debt securities and other fixed-income
securities including corporate bonds and notes, government securities and
indexed/structured securities. Balanced Portfolio may invest in the types of
investments previously described under "Growth Portfolios" on page 8. Although
the Portfolio places some emphasis on the income objective, investors should
keep in mind that Balanced Portfolio is not designed to produce a consistent
level of income.

THE FOLLOWING QUESTIONS ARE DESIGNED TO HELP YOU BETTER UNDERSTAND AN INVESTMENT
IN BALANCED PORTFOLIO.

Q: HOW ARE ASSETS ALLOCATED BETWEEN THE GROWTH AND INCOME COMPONENTS OF
BALANCED PORTFOLIO?

A: Balanced Portfolio may invest in a combination of common stocks, preferred
stocks, convertible securities, debt securities and other fixed-income
securities. Balanced Portfolio may shift assets between the growth and income
components of its portfolio based on the portfolio manager's analysis of
relevant market, financial and economic conditions. If the portfolio manager
believes that growth securities will provide better returns than the yields then
available or expected on income-producing securities, the Portfolio will place a
greater emphasis on the growth component.

Q: WHAT TYPES OF SECURITIES MAKE UP THE GROWTH COMPONENT OF BALANCED
PORTFOLIO?

Q: WHAT TYPES OF SECURITIES MAKE UP THE INCOME COMPONENT OF BALANCED
PORTFOLIO?

A: The income component of Balanced Portfolio will consist of securities that
the portfolio manager believes have income potential. Such securities may
include equity securities, convertible securities and all types of debt
securities. Equity securities may be included in the income component of
Balanced Portfolio if they currently pay dividends or a portfolio manager
believes they have the potential for either increasing their dividends or
commencing dividends, if none are currently paid.

10 JANUS ASPEN SERIES PROSPECTUS MAY 1, 1998
<PAGE>

the Portfolio was not hedged or remained more fully invested in stocks or bonds.

DIVERSIFICATION
The Investment Company Act of 1940 (the "1940 Act") classifies investment
companies as either diversified or nondiversified. All of the Portfolios (except
Aggressive Growth Portfolio) qualify as diversified funds under the 1940 Act and
are subject to the following diversification requirements: