MUNICIPAL INVT TR FD AMT MON PYMT SER 100 DEFINED ASSET FDS
485BPOS, 1999-11-29
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<PAGE>
   AS FILED WITH THE SECURITIES AND EXCHANGE COMMISSION ON NOVEMBER 29, 1999

                                                       REGISTRATION NO. 33-48867
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------

                       SECURITIES AND EXCHANGE COMMISSION

                             WASHINGTON, D.C. 20549

                   ------------------------------------------

                         POST-EFFECTIVE AMENDMENT NO. 2

                                       TO

                                    FORM S-6

                   ------------------------------------------

                   FOR REGISTRATION UNDER THE SECURITIES ACT

                    OF 1933 OF SECURITIES OF UNIT INVESTMENT

                        TRUSTS REGISTERED ON FORM N-8B-2

                   ------------------------------------------

A. EXACT NAME OF TRUST:

                        MUNICIPAL INVESTMENT TRUST FUND

                        AMT MONTHLY PAYMENT SERIES--100

                              DEFINED ASSET FUNDS

B. NAME OF DEPOSITOR:

                   MERRILL LYNCH, PIERCE, FENNER & SMITH INC.

                           SALOMON SMITH BARNEY INC.

                       PRUDENTIAL SECURITIES INCORPORATED

                            PAINEWEBBER INCORPORATED

                           DEAN WITTER REYNOLDS INC.

C. COMPLETE ADDRESSES OF DEPOSITORS' PRINCIPAL EXECUTIVE OFFICES:


 MERRILL LYNCH, PIERCE,
     FENNER & SMITH
      INCORPORATED
   DEFINED ASSET FUNDS
  POST OFFICE BOX 9051
PRINCETON, NJ 08543-9051                          SALOMON SMITH BARNEY INC.
                                                        388 GREENWICH
                                                     STREET--23RD FLOOR
                                                     NEW YORK, NY 10013



  PRUDENTIAL SECURITIES  PAINEWEBBER INCORPORATED DEAN WITTER REYNOLDS INC.
      INCORPORATED          1285 AVENUE OF THE         TWO WORLD TRADE
   ONE NEW YORK PLAZA            AMERICAS            CENTER--59TH FLOOR
   NEW YORK, NY 10292       NEW YORK, NY 10019       NEW YORK, NY 10048


D. NAMES AND COMPLETE ADDRESSES OF AGENTS FOR SERVICE:


  TERESA KONCICK, ESQ.      LEE B. SPENCER, JR.       ROBERT E. HOLLEY
      P.O. BOX 9051         ONE NEW YORK PLAZA        1200 HARBOR BLVD.
PRINCETON, NJ 08543-9051    NEW YORK, NY 10292       WEEHAWKEN, NJ 07087

                                COPIES TO:           DOUGLAS LOWE, ESQ.
                          PIERRE DE SAINT PHALLE, DEAN WITTER REYNOLDS INC.
    MICHAEL KOCHMANN               ESQ.                TWO WORLD TRADE
    388 GREENWICH ST.      450 LEXINGTON AVENUE      CENTER--59TH FLOOR
   NEW YORK, NY 10013       NEW YORK, NY 10017       NEW YORK, NY 10048


The issuer has registered an indefinite number of Units under the Securities Act
of 1933 pursuant to Rule 24f-2 and filed the Rule 24f-2 Notice for the most
recent fiscal year on March 11, 1999.

Check box if it is proposed that this filing will become effective on November
30, 1999 pursuant to paragraph (b) of Rule 485.  / x /

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<PAGE>
<PAGE>
                                     DEFINED ASSET FUNDSSM
- --------------------------------------------
- -----------------------------------


                              MUNICIPAL INVESTMENT TRUST FUND
                              AMT MONTHLY PAYMENT SERIES--100
                              (A UNIT INVESTMENT TRUST)
                              O   PORTFOLIO OF LONG TERM MUNICIPAL BONDS
                              O   DESIGNED FOR INCOME FREE FROM REGULAR FEDERAL
                                  INCOME TAX
                              O   MONTHLY INCOME DISTRIBUTIONS
                              O   AMT BONDS



SPONSORS:
Merrill Lynch,
Pierce, Fenner & Smith         -------------------------------------------------
    Incorporated               The Securities and Exchange Commission has not
Salomon Smith Barney Inc.      approved or disapproved these Securities or
PaineWebber Incorporated       passed upon the adequacy of this prospectus. Any
Dean Witter Reynolds Inc.      representation to the contrary is a criminal
Prudential Securities          offense.
Incorporated                   Prospectus dated November 30, 1999.


<PAGE>
- --------------------------------------------------------------------------------

Defined Asset FundsSM
Defined Asset FundsSM is America's oldest and largest family of unit investment
trusts, with over $160 billion sponsored over the last 28 years. Defined Asset
Funds has been a leader in unit investment trust research and product
innovation. Our family of Funds helps investors work toward their financial
goals with a full range of quality investments, including municipal, corporate
and government bond portfolios, as well as domestic and international equity
portfolios.

Defined Asset Funds offer a number of advantages:
   o A disciplined strategy of buying and holding with a long-term view is the
     cornerstone of Defined Asset Funds.
   o Fixed portfolio: Defined Funds follow a buy and hold investment strategy;
     funds are not managed and portfolio changes are limited.
o Defined Portfolios: We choose the stocks and bonds in advance, so you know
  what you're investing in.
o Professional research: Our dedicated research team seeks out stocks or bonds
      appropriate for a particular fund's objectives.
o Ongoing supervision: We monitor each portfolio on an ongoing basis.
No matter what your investment goals, tolerance for risk or time horizon,
there's probably a Defined Asset Fund that suits your investment style. Your
financial professional can help you select a Defined Asset Fund that works best
for your investment portfolio.

THE FINANCIAL INFORMATION IN THIS PROSPECTUS IS AS OF THE EVALUATION DATE, JULY
31, 1999.


CONTENTS
                                                              PAGE
                                                         ---------
Risk/Return Summary....................................          3
What You Can Expect From Your Investment...............          7
   Monthly Income......................................          7
   Return Figures......................................          7
   Records and Reports.................................          7
The Risks You Face.....................................          8
   Interest Rate Risk..................................          8
   Call Risk...........................................          8
   Reduced Diversification Risk........................          8
   Liquidity Risk......................................          8
   Concentration Risk..................................          8
   Bond Quality Risk...................................          9
   Insurance Related Risk..............................          9
   Litigation and Legislation Risks....................          9
Selling or Exchanging Units............................          9
   Sponsors' Secondary Market..........................          9
   Selling Units to the Trustee........................         10
   Exchange Option.....................................         10
How The Fund Works.....................................         11
   Pricing.............................................         11
   Evaluations.........................................         11
   Income..............................................         11
   Expenses............................................         11
   Portfolio Changes...................................         12
   Fund Termination....................................         12
   Certificates........................................         13
   Trust Indenture.....................................         13
   Legal Opinion.......................................         14
   Auditors............................................         14
   Sponsors............................................         14
   Trustee.............................................         14
   Underwriters' and Sponsors' Profits.................         14
   Public Distribution.................................         15
   Code of Ethics......................................         15
   Year 2000 Issues....................................         15
Taxes..................................................         15
Supplemental Information...............................         16
Financial Statements...................................        D-1


                                       2
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RISK/RETURN SUMMARY


       1.  WHAT IS THE FUND'S OBJECTIVE?
           The Fund seeks interest income that is exempt from regular
           federal income taxes for investors who are not subject to
           Alternative Minimum Tax (AMT) by investing in a fixed
           portfolio consisting primarily of municipal revenue bonds
           with an estimated average life of 27 years. Interest on
           certain of the bonds will be a preference item for AMT.
       2.  WHAT ARE MUNICIPAL REVENUE BONDS?
           Municipal revenue bonds are bonds issued by states,
           municipalities and public authorities to finance the cost
           of buying, building or improving various projects intended
           to generate revenue, such as airports, health care
           facilities, housing and municipal electric, water and sewer
           utilities. Generally, payments on these bonds depend solely
           on the revenues generated by the projects, excise taxes or
           state appropriations, and are not backed by the
           government's taxing power.
       3.  WHAT IS THE FUND'S INVESTMENT STRATEGY?
        O  The Fund plans to hold to maturity 11 long-term tax-exempt
           municipal bonds, and some short-term bonds reserved to pay
           the deferred sales fee, with a current aggregate face
           amount of $6,825,000. The Fund is a unit investment trust
           which means that, unlike a mutual fund, the Fund's
           portfolio is not managed.
        o  When the bonds were initially deposited (August 8, 1997),
           they were rated A or better by Standard & Poor's, Moody's
           or Fitch, or in the opinion of the agent for the Sponsors
           had similar credit quality to bonds rated A or better. The
           credit quality of the bonds may currently be lower.
        o  Many of the bonds can be called at a premium declining over
           time to par value. Some bonds may be called earlier at par
           for extraordinary reasons.
        o  34% of the bonds are insured by insurance companies.
           Insurance guarantees timely payments of principal and
           interest on the bonds (but not Fund units or the market
           value of the bonds before they mature).

           The Portfolio consists of municipal bonds of the following
           types:



                                                 APPROXIMATE
                                                  PORTFOLIO
                                                  PERCENTAGE



o          Airports/Ports/Highways                       17%
o          General Obligation                               2%
        o  Hospital/Health Care                           16%
        o  Housing                                          52%
o          Lease Rental Appropriation                     5%
o          Universities/Colleges                             8%



       4.  WHAT ARE THE SIGNIFICANT RISKS?
           YOU CAN LOSE MONEY BY INVESTING IN THE FUND. THIS CAN
           HAPPEN FOR VARIOUS REASONS, INCLUDING:
        o  Rising interest rates, an issuer's worsening financial
           condition or a drop in bond ratings can reduce the price of
           your units.
        o  Because the Fund is concentrated in housing bonds, adverse
           developments in this sector may affect the value of your
           units.
        o  Assuming no changes in interest rates, when you sell your
           units, they will generally be worth less than your cost
           because your cost included a sales fee.
        o  The Fund will receive early returns of principal if bonds
           are called or sold before they mature. If this happens your
           income will decline and you may not be able to reinvest the
           money you receive at as high a yield or as long a maturity.



       5.  IS THIS FUND APPROPRIATE FOR YOU?
           Yes, if you want monthly income free from regular federal
           income tax. You will benefit from a professionally selected
           and supervised portfolio whose risk is reduced by investing
           in bonds of several different issuers.
           The Fund is not appropriate for you if you want a
           speculative investment that changes to take advantage of
           market movements, if you are subject to AMT, if you do not
           want a tax-advantaged investment or if you cannot tolerate
           any risk.


                                       3
<PAGE>

           DEFINING YOUR INCOME


           WHAT YOU MAY EXPECT (PAYABLE ON THE 25TH DAY OF
           EACH MONTH):
           Regular Monthly Income per unit                   $    3.82
           Annual Income per unit                            $   45.88
           RECORD DAY: 10th day of each month
           These figures are estimates on the evaluation date; actual
           payments may vary.



       6.  WHAT ARE THE FUND'S FEES AND EXPENSES?
           This table shows the costs and expenses you may pay,
           directly or indirectly, when you invest in the Fund.
           INVESTOR FEES
           Maximum Sales Fee (Load) on new
           purchases (as a percentage of
           $1,000 invested)                                2.90%
           You will pay an up-front sales fee of 1.125% as well as a
           deferred sales fee of $3.75 per unit quarterly November,
           February, May and August, through August, 2000.
           Employees of some of the Sponsors and their affiliates may
           be charged a reduced sales fee of no less than $5.00 per
           Unit.
           The maximum sales fee is reduced if you invest at least
           $100,000, as follows:



                                                 YOUR MAXIMUM
                                                    SALES FEE
                     IF YOU INVEST:                  WILL BE:
           -----------------------------------  -----------------
           Less than $100,000                            2.90%
           $100,000 to $249,999                          2.65%
           $250,000 to $499,999                          2.40%
           $500,000 to $999,999                          2.15%
           $1,000,000 and over                           1.90%

           Maximum Exchange Fee                          1.90%


           ESTIMATED ANNUAL FUND OPERATING EXPENSES


                                                                        AMOUNT
                                                                      PER UNIT
                                                                    -----------
                                                         $    0.62
           Trustee's Fee
                                                         $    0.41
           Portfolio Supervision,
           Bookkeeping and
           Administrative Fees
           (including updating
           expenses)
                                                         $    0.17
           Evaluator's Fee
                                                         $    0.20
           Organization Costs
                                                         $    0.56
           Other Operating Expenses
                                                        -----------
                                                         $    1.96
           TOTAL



           The Sponsors historically paid organization costs and
           updating expenses.
       7.  HOW HAVE SIMILAR FUNDS PERFORMED IN THE PAST?
           In the following chart we show past performance of prior
           Monthly Payment Series, which had the same investment
           objectives, strategies and types of bonds as this Fund.
           These prior series differed in that they charged a higher
           sales fee. These prior Monthly Payment Series were offered
           between February 4, 1988 and September 26, 1996 and were
           outstanding on June 30, 1999. OF COURSE, PAST PERFORMANCE
           OF PRIOR SERIES IS NO GUARANTEE OF FUTURE RESULTS OF THIS
           FUND.

           AVERAGE ANNUAL COMPOUND TOTAL RETURNS
           FOR PRIOR SERIES
           Reflecting all expenses. For periods ended 6/30/99.



                   WITH SALES FEE                    NO SALES FEE
            1 YEAR     5 YEARS   10 YEARS    1 YEAR     5 YEARS   10 YEARS


- -------------------------------------------------------------------


High         2.84%      7.24%      6.16%      4.27%      8.44%      6.75%
Average      -0.53      5.31       5.95       2.64       6.33       6.54
Low          -5.19      3.46       5.71       -0.11      4.45       6.30


- -------------------------------------------------------------------


Average
Sales fee    3.25%      5.03%      5.82%


- -------------------------------------------------------------------

Note: All returns represent changes in unit price with distributions reinvested
 into the Municipal Fund Investment Accumulation Program.


       8.  IS THE FUND MANAGED?
           Unlike a mutual fund, the Fund is not managed and bonds are
           not sold because of market changes. Rather, experienced
           Defined Asset Funds financial analysts regularly review the
           bonds in the Fund. The Fund may sell a bond if certain
           adverse credit or other conditions exist.
       9.  HOW DO I BUY UNITS?
           The minimum investment is one unit.
           You can buy units from any of the Sponsors and other
           broker-dealers. The Sponsors are listed later in this
           prospectus. Some banks may offer units for sale through
           special arrangements with the Sponsors, although certain
           legal restrictions may apply.


                                       4
<PAGE>
           UNIT PRICE PER UNIT                       $881.52
           (as of July 31, 1999)
           Unit price is based on the net asset value of the Fund plus
           the sales fee. An amount equal to any principal cash, as
           well as net accrued but undistributed interest on the unit,
           is added to the unit price. An independent evaluator prices
           the bonds at 3:30 p.m. Eastern time every business day.
           Unit price changes every day with changes in the prices of
           the bonds in the Fund.

      10.  HOW DO I SELL UNITS?
           You may sell your units at any time to any
           Sponsor or the Trustee for the net asset
           value determined at the close of business on
           the date of sale, less any remaining deferred
           sales fee. You will not pay any other fee
           when you sell your units.
      11.  HOW ARE DISTRIBUTIONS MADE AND TAXED?
           The Fund pays income monthly. In the opinion of bond
           counsel when each bond was issued, interest on the bonds in
           this Fund is generally 100% exempt from regular federal
           income tax. Interest on approximately 69% of the bonds will
           be a preference item for purposes of AMT.
           A portion of the income may also be exempt from state and
           local personal income taxes, depending on where you live.
           You will also receive principal payments if bonds are sold,
           called or mature, when the cash available is more than
           $5.00 per unit. You will be subject to tax on any gain
           realized by the Fund on the disposition of bonds.
      12.  WHAT OTHER SERVICES ARE AVAILABLE?
           REINVESTMENT
           You will receive your monthly income in cash unless you
           choose to compound your income by reinvesting with no sales
           fee in the Municipal Fund Investment Accumulation Program,
           Inc. This program is an open-end mutual fund with a
           comparable investment objective. Income from this program
           will generally be subject to state and local income taxes,
           but most or all of the income will not be subject to AMT.
           For more complete information about the program, including
           charges and fees, ask the Trustee for the Program's
           prospectus. Read it carefully before you invest. The
           Trustee must receive your written election to reinvest at
           least 10 days before the record day of an income payment.
           EXCHANGE PRIVILEGES
           You may exchange units of this Fund for units of certain
           other Defined Asset Funds. You may also exchange into this
           Fund from certain other funds. We charge a reduced sales
           fee on exchanges.

                                       5
<PAGE>
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    TAX-FREE VS. TAXABLE INCOME: A COMPARISON OF TAXABLE AND TAX-FREE YIELDS

<TABLE>
<CAPTION>

                                  EFFECTIVE
TAXABLE INCOME 1999*               % TAX                         TAX-FREE YIELD OF
  SINGLE RETURN    JOINT RETURN   BRACKET    3%     3.5%     4%     4.5%     5%     5.5%     6%     6.5%
                                                        IS EQUIVALENT TO A TAXABLE YIELD OF
- ----------------------------------------------------------------------------------------------------------
<S>        <C>    <C>       <C>      <C>       <C>    <C>      <C>    <C>      <C>     <C>     <C>     <C>
 $      0- 25,750 $      0- 43,050   15.00     3.53   4.12     4.71   5.29     5.88    6.47    7.06    7.65
- ----------------------------------------------------------------------------------------------------------
$ 25,751- 62,450 $ 43,051-104,050   28.00     4.17   4.86     5.56   6.25     6.94    7.64    8.33    9.03
- ----------------------------------------------------------------------------------------------------------
$ 62,451-130,250 $104,051-158,550   31.00     4.35   5.07     5.80   6.52     7.25    7.97    8.70    9.42
- ----------------------------------------------------------------------------------------------------------
$130,251-283,150 $158,551-283,150   36.00     4.69   5.47     6.25   7.03     7.81    8.59    9.38   10.16
- ----------------------------------------------------------------------------------------------------------
OVER $283,151       OVER $283,151   39.60     4.97   5.79     6.62   7.45     8.28    9.11    9.93   10.76
- ----------------------------------------------------------------------------------------------------------
</TABLE>


To compare the yield of a taxable security with the yield of a federally
tax-free security, find your taxable income and read across. The table
incorporates 1999 federal income tax rates and assumes that all income would
otherwise be taxed at a U.S. investor's highest tax rate. Yield figures are for
example only.

*Based upon net amount subject to federal income tax after deductions and
exemptions. This table does not reflect the possible effect of other tax
factors, such as alternative minimum tax, personal exemptions, the phase-out of
exemptions, itemized deductions, the possible partial disallowance of deductions
or state and local taxation. Consequently, investors are urged to consult their
own tax advisers in this regard.

                MUNICIPAL BONDS AND THE ALTERNATIVE MINIMUM TAX


      INCOME+        MAXIMUM 'PREFERENCE' INCOME
                        WITHOUT TRIGGERING AMT
                       (STATE INCOME TAX RATES)
SINGLE ++ JOINT ++      0%        7%       11%
- --------------------------------------------------
          $50,000    $21,000   $16,000   $14,000
- --------------------------------------------------
$30,000              $20,000   $16,000   $15,000
- --------------------------------------------------
          $100,000   $25,000   $16,000   $12,000
- --------------------------------------------------
$55,000              $22,000   $16,000   $14,000
- --------------------------------------------------
          $225,000   $31,000   $14,000    $5,000
- --------------------------------------------------
$205,000             $31,000   $15,000    $7,000
- --------------------------------------------------


NOTES:
+ Regular taxable income plus state income
  taxes and personal exemptions.
 ++ Assuming no dependents.
Under federal tax law, interest income on certain municipal bonds, although
exempt from regular income tax, is treated as a 'preference' item for purposes
of AMT. The table above shows amounts of such municipal bond 'preference'
interest income, assuming no other 'preference' or similar items apply, that
individual taxpayers could receive in 1998 without becoming subject to the AMT.
The table gives information for single and joint returns of U.S. individuals
having no dependents. The table provides three income levels and three
hypothetical state income tax rates. The table further assumes that the stated
amount of municipal bond 'preference' interest income is subject to state income
taxes.

                                       6
<PAGE>
WHAT YOU CAN EXPECT FROM YOUR INVESTMENT

MONTHLY INCOME

The Fund will pay you regular monthly income. Your monthly income may vary
because of:
   o elimination of one or more bonds from the Fund's portfolio because of
     calls, redemptions or sales;
   o a change in the Fund's expenses; or
   o the failure by a bond's issuer to pay interest.

Changes in interest rates generally will not affect your monthly income because
the portfolio is fixed.

Along with your monthly income, you will receive your share of any available
bond principal.

RETURN FIGURES

We cannot predict your actual return, which will vary with unit price, how long
you hold your investment and changes in the portfolio, interest income and
expenses.

Estimated Current Return equals the estimated annual cash to be received from
the bonds in the Fund less estimated annual Fund expenses, divided by the Unit
Price (including the maximum sales fee):


 Estimated Annual                  Estimated
 Interest Income        -       Annual Expenses
- -------------------------------------------------
                   Unit Price


Estimated Long Term Return is a measure of the estimated return over the
estimated life of the Fund. Unlike Estimated Current Return, Estimated Long Term
Return reflects maturities, discounts and premiums of the bonds in the Fund. It
is an average of the yields to maturity (or in certain cases, to an earlier call
date) of the individual bonds in the portfolio, adjusted to reflect the Fund's
maximum sales fee and estimated expenses. We calculate the average yield for the
portfolio by weighting each bond's yield by its market value and the time
remaining to the call or maturity date.

Yields on individual bonds depend on many factors including general conditions
of the bond markets, the size of a particular offering and the maturity and
quality rating of the particular issues. Yields can vary among bonds with
similar maturities, coupons and ratings.

These return quotations are designed to be comparative rather than predictive.

RECORDS AND REPORTS

You will receive:
o a monthly statement of income payments and any principal payments;
o a notice from the Trustee when new bonds are deposited in exchange or
  substitution for bonds originally deposited;
o an annual report on Fund activity; and
o annual tax information. This will also be sent to the IRS. You must report the
  amount of tax-exempt interest received during the year.

You may request:
o copies of bond evaluations to enable you to comply with federal and state tax
  reporting requirements; and
o audited financial statements of the Fund.

You may inspect records of Fund transactions at the Trustee's office during
regular business hours.

                                       7
<PAGE>
THE RISKS YOU FACE

INTEREST RATE RISK

Investing involves risks, including the risk that your investment will decline
in value if interest rates rise. Generally, bonds with longer maturities will
change in value more than bonds with shorter maturities. Bonds in the Fund are
more likely to be called when interest rates decline. This would result in early
returns of principal to you and may result in early termination of the Fund. Of
course, we cannot predict how interest rates may change.

CALL RISK

Many bonds can be prepaid or 'called' by the issuer before their stated
maturity. For example, some bonds may be required to be called pursuant to
mandatory sinking fund provisions.

Also, an issuer might call its bonds during periods of falling interest rates,
if the issuer's bonds have a coupon higher than current market rates.

An issuer might call its bonds in extraordinary cases, including if:
   o it no longer needs the money for the original purpose;
   o the project is condemned or sold;
   o the project is destroyed and insurance proceeds are used to redeem the
     bonds;
   o any related credit support expires and is not replaced; or
   o interest on the bonds become taxable.

If the bonds are called, your income will decline and you may not be able to
reinvest the money you receive at as high a yield or as long a maturity. An
early call at par of a premium bond will reduce your return.

REDUCED DIVERSIFICATION RISK

If many investors sell their units, the Fund will have to sell bonds. This could
reduce the diversification of your investment and increase your share of Fund
expenses.

LIQUIDITY RISK

The bonds will generally trade in the over-the-counter market. We cannot assure
you that a liquid trading market will exist, especially since current law may
restrict the Fund from selling bonds to any Sponsor. The value of the bonds, and
of your investment, may be reduced if trading in bonds is limited or absent.

CONCENTRATION RISK

When a certain type of bond makes up 25% or more of the portfolio, the Fund is
said to be 'concentrated' in that bond type, which makes the Fund less
diversified.

Here is what you should know about the Fund's concentration in housing bonds.
Multi-family housing revenue bonds and single family mortgage revenue bonds are
issued to provide financing for various housing projects. These bonds are
payable primarily from the revenue derived from mortgage loans to housing
projects for low to moderate income familities or notes secured by mortgages on
residences. Repayment of these bonds is dependent upon, among other things:
   o occupany levels;
   o rental income;
   o the default rate on the underlying mortgage loans;
   o the ability of mortgage insurers to pay claims;
   o the continued availability of federal, state or local housing subsidiary
     programs;
   o economic conditions in local markets;
   o construction costs;

                                       8
<PAGE>
   o taxes;
   o utility costs;
   o the level of operating expenses; and
   o the managerial ability of project managers.

Housing bonds generally may be prepaid at any time. Therefore, their average
life will ordinarily be less then their stated maturity.

Changes to the portfolio from bond redemptions, maturities and sales may affect
the Fund's concentration over time.

BOND QUALITY RISK

A reduction in a bond's rating may decrease its value and, indirectly, the value
of your investment in the Fund.

INSURANCE RELATED RISK

Some bonds may be backed by insurance companies (as shown under Portfolio).
Insurance policies generally make payments only according to a bond's original
payment schedule and do not make early payments when a bond defaults or becomes
taxable. Although the federal government does not regulate the insurance
business, various state laws and federal initiatives and tax law changes could
significantly affect the insurance business. The claims-paying ability of the
insurance companies is generally rated A or better by Standard & Poor's or
another nationally recognized rating organization. The insurance company ratings
are subject to change at any time at the discretion of the rating agencies.

LITIGATION AND LEGISLATION RISKS

We do not know of any pending litigation that might have a material adverse
effect upon the Fund.

Future tax legislation could affect the value of the portfolio by:
   o limiting real property taxes,
   o reducing tax rates,
   o imposing a flat or other form of tax, or
   o exempting investment income from tax.

SELLING OR EXCHANGING UNITS

You can sell your units at any time for a price based on net asset value. Your
net asset value is calculated each business day by:
   o adding the value of the bonds, net accrued interest, cash and any other
     Fund assets;
   o subtracting accrued but unpaid Fund expenses, unreimbursed Trustee
      advances, cash held to buy back units or for distribution to investors and
     any other Fund liabilities; and
   o dividing the result by the number of outstanding units.

Your net asset value when you sell may be more or less than your cost because of
sales fees, market movements and changes in the portfolio.

If you sell your units before the final deferred sales fee installment, the
amount of any remaining installments will be deducted from your proceeds.

SPONSORS' SECONDARY MARKET

While we are not obligated to do so, we will buy back units at net asset value
without any other fee or charge other than any remaining deferred sales fee. We
may resell the units to other buyers or to the Trustee. You should consult your
financial professional for current market prices to determine if other broker-
dealers or banks are offering higher prices.

                                       9
<PAGE>
We have maintained a secondary market continuously for over 25 years, but we
could discontinue it without prior notice for any business reason.

SELLING UNITS TO THE TRUSTEE

Regardless of whether we maintain a secondary market, you can sell your units to
the Trustee at any time by sending the Trustee a letter (with any outstanding
certificates if you hold unit certificates). You must properly endorse your
certificates (or execute a written transfer instrument with signatures
guaranteed by an eligible institution). Sometimes, additional documents are
needed such as a trust document, certificate of corporate authority, certificate
of death or appointment as executor, administrator or guardian.

Within seven days after your request and the necessary documents are received,
the Trustee will mail a check to you. Contact the Trustee for additional
information.

As long as we are maintaining a secondary market, the Trustee will sell your
units to us at a price based on net asset value. If there is no secondary
market, the Trustee may sell your units in the over-the-counter market for a
higher price, but it is not obligated to do so. In that case, you will receive
the net proceeds of the sale.

If the Fund does not have cash available to pay you for units you are selling,
the agent for the Sponsors will select bonds to be sold. Bonds will be selected
based on market and credit factors. These sales could be made at times when the
bonds would not otherwise be sold and may result in your receiving less than the
unit par value and also reduce the size and diversity of the Fund.

If you acquire 25% or more of the outstanding units of the Fund and you sell
units with a value exceeding $250,000, the Trustee may choose to pay you 'in
kind' by distributing bonds and cash with a total value equal to the price of
those units. The Trustee will try to distribute bonds in the portfolio pro rata,
but it reserves the right to distribute only one or a few bonds. The Trustee
will act as your agent in an in kind distribution and will either hold the bonds
for your account or sell them as you instruct. You must pay any transaction
costs as well as transfer and ongoing custodial fees on sales of bonds
distributed in kind.

There could be a delay in paying you for your units:
   o if the New York Stock Exchange is closed (other than customary weekend and
      holiday closings);
   o if the SEC determines that trading on the New York Stock Exchange is
     restricted or that an emergency exists making sale or evaluation of the
     bonds not reasonably practicable; and
   o for any other period permitted by SEC order.

EXCHANGE OPTION

You may exchange units of certain Defined Asset Funds for units of this Fund at
a maximum exchange fee of 1.90%. You may exchange units of this Fund for units
of certain other funds at a reduced sales fee if your investment goals change.
To exchange units, you should talk to your financial professional about what
funds are exchangeable, suitable and currently available.

Normally, an exchange is taxable and you must recognize any gain or loss on the

                                       10
<PAGE>
exchange. However, the IRS may try to disallow a loss if the portfolios of the
two funds are not materially different; you should consult your own tax adviser.

We may amend or terminate this exchange option at any time without notice.

HOW THE FUND WORKS

PRICING

The price of a unit includes interest accrued on the bonds, less expenses, from
the most recent Record Day up to, but not including, the settlement date, which
is usually three business days after the purchase date of the unit.

A portion of the price of a unit consists of cash so that the Trustee can
provide you with regular monthly income. When you sell your units you will
receive your share of this cash.

In addition, as with mutual funds, the Fund (and therefore the investors) pay
all or some of the costs of organizing the Fund including:
   o cost of initial preparation of legal documents;
   o federal and state registration fees;
   o initial fees and expenses of the Trustee;
   o initial audit; and
   o legal expenses and other out-of-pocket expenses.

These costs are amortized over the first five years of the Fund.

EVALUATIONS

An independent Evaluator values the bonds on each business day (excluding
Saturdays, Sundays and the following holidays as observed by the New York Stock
Exchange: New Year's Day, Presidents' Day, Martin Luther King, Jr. Day, Good
Friday, Memorial Day, Independence Day, Labor Day, Thanksgiving and Christmas).
Bond values are based on current bid or offer prices for the bonds or comparable
bonds. In the past, the difference between bid and offer prices of publicly
offered tax-exempt bonds has ranged from 0.5% of face amount on actively traded
issues to 3.5% on inactively traded issues; the difference has averaged between
1 and 2%.

INCOME

The Trustee credits interest to an Income Account and other receipts to a
Capital Account. The Trustee may establish a Reserve Account by withdrawing from
these accounts amounts it considers appropriate to pay any material liability.
These accounts do not bear interest.

EXPENSES

The Trustee is paid monthly. It also benefits when it holds cash for the Fund in
non-interest bearing accounts. The Trustee may also receive additional amounts:
   o to reimburse the Trustee for the Fund's operating expenses;
   o for extraordinary services and costs of indemnifying the Trustee and the
      Sponsors;
   o costs of actions taken to protect the Fund and other legal fees and
     expenses;
   o expenses for keeping the Fund's registration statement current; and
   o Fund termination expenses and any governmental charges.

The Sponsors are currently reimbursed up to 55 cents per $1,000 face amount
annually for providing portfolio supervisory, bookkeeping and administrative
services and for any other

                                       11
<PAGE>
expenses properly chargeable to the Fund. Legal, typesetting, electronic filing
and regulatory filing fees and expenses associated with updating the Portfolio's
registration statement yearly are also now chargeable to the Portfolio. While
this fee may exceed the amount of these costs and expenses attributable to this
Fund, the total of these fees for all Series of Defined Asset Funds will not
exceed the aggregate amount attributable to all of these Series for any calendar
year. The Fund also pays the Evaluator's fees.

The Trustee's, Sponsors' and Evaluator's fees may be adjusted for inflation
without investors' approval.

Any quarterly deferred sales charges you owe are paid with interest and
principal from certain bonds. If these amounts are not enough, the rest will be
paid out of distributions to you from the Fund's Capital and Income Accounts.

The Sponsors will pay advertising and selling expenses at no charge to the Fund.
If Fund expenses exceed initial estimates, the Fund will owe the excess. The
Trustee has a lien on Fund assets to secure reimbursement of Fund expenses and
may sell bonds if cash is not available.

PORTFOLIO CHANGES

The Sponsors and Trustee are not liable for any default or defect in a bond.

Unlike a mutual fund, the portfolio is designed to remain intact and we may keep
bonds in the portfolio even if their credit quality declines or other adverse
financial circumstances occur. However, we may sell a bond in certain cases if
we believe that certain adverse credit conditions exist or if a bond becomes
taxable.

If we maintain a secondary market in units but are unable to sell the units that
we buy in the secondary market, we will redeem units, which will affect the size
and composition of the portfolio. Units offered in the secondary market may not
represent the same face amount of bonds that they did originally.

We decide whether or not to offer units for sale that we acquire in the
secondary market after reviewing:
   o diversity of the portfolio;
   o size of the Fund relative to its original size;
   o ratio of Fund expenses to income;
   o current and long-term returns;
   o degree to which units may be selling at a premium over par; and
   o cost of maintaining a current prospectus.

FUND TERMINATION

The Fund will terminate following the stated maturity or sale of the last bond
in the portfolio. The Fund may also terminate earlier with the consent of
investors holding 51% of the units or if total assets of the Fund have fallen
below 40% of the face amount of bonds deposited. We will decide whether to
terminate the Fund early based on the same factors used in deciding whether or
not to offer units in the secondary market.

When the Fund is about to terminate you will receive a notice, and you will be
unable to sell your units after that time. On or shortly before termination, we
will sell any remaining bonds, and you will receive your final distribution. Any
bond that cannot be sold at a reasonable

                                       12
<PAGE>
price may continue to be held by the Trustee in a liquidating trust pending its
final sale.

You will pay your share of the expenses associated with termination, including
brokerage costs in selling bonds. This may reduce the amount you receive as your
final distribution.

CERTIFICATES

Certificates for units are issued on request. You may transfer certificates by
complying with the requirements for redeeming certificates, described above. You
can replace lost or mutilated certificates by delivering satisfactory indemnity
and paying the associated costs.

TRUST INDENTURE

The Fund is a 'unit investment trust' governed by a Trust Indenture, a contract
among the Sponsors, the Trustee and the Evaluator, which sets forth their duties
and obligations and your rights. A copy of the Indenture is available to you on
request to the Trustee. The following summarizes certain provisions of the
Indenture.

The Sponsors and the Trustee may amend the Indenture without your consent:
   o to cure ambiguities;
   o to correct or supplement any defective or inconsistent provision;
   o to make any amendment required by any governmental agency; or
   o to make other changes determined not to be materially adverse to your best
     interest (as determined by the Sponsors).

Investors holding 51% of the units may amend the Indenture. Every investor must
consent to any amendment that changes the 51% requirement. No amendment may
reduce your interest in the Fund without your written consent.

The Trustee may resign by notifying the Sponsors. The Sponsors may remove the
Trustee without your consent if:
   o it fails to perform its duties and the Sponsors determine that its
     replacement is in your best interest; or
   o it becomes incapable of acting or bankrupt or its affairs are taken over by
      public authorities.
Investors holding 51% of the units may remove the Trustee. The Evaluator may
resign or be removed by the Sponsors and the Trustee without the consent of
investors. The resignation or removal of either becomes effective when a
successor accepts appointment. The Sponsors will try to appoint a successor
promptly; however, if no successor has accepted within 30 days after notice of
resignation, the resigning Trustee or Evaluator may petition a court to appoint
a successor.

Any Sponsor may resign as long as one Sponsor with a net worth of $2 million
remains and agrees to the resignation. The remaining Sponsors and the Trustee
may appoint a replacement. If there is only one Sponsor and it fails to perform
its duties or becomes bankrupt the Trustee may:
   o remove it and appoint a replacement Sponsor;
   o liquidate the Fund; or
   o continue to act as Trustee without a Sponsor.

Merrill Lynch, Pierce, Fenner & Smith Incorporated acts as agent for the
Sponsors.

The Trust Indenture contains customary provisions limiting the liability of the
Trustee, the Sponsors and the Evaluator.

                                       13
<PAGE>
LEGAL OPINION

Davis Polk & Wardwell, 450 Lexington Avenue, New York, New York 10017, as
special counsel for the Sponsors, has given an opinion that the units are
validly issued.

AUDITORS

Deloitte & Touche LLP, 2 World Financial Center, New York, New York 10281,
independent accountants, audited the Statement of Condition included in this
prospectus.

SPONSORS

The Sponsors are:

MERRILL LYNCH, PIERCE, FENNER & SMITH INCORPORATED (a wholly-owned subsidiary of
Merrill Lynch & Co., Inc.)
P.O. Box 9051,
Princeton, NJ 08543-9051

SALOMON SMITH BARNEY INC. (an indirectly wholly-owned subsidiary of Citigroup
Inc.)
388 Greenwich Street--23rd Floor,
New York, NY 10013

DEAN WITTER REYNOLDS INC. (a principal operating subsidiary of Morgan Stanley
Dean Witter & Co.)
Two World Trade Center--59th Floor,
New York, NY 10048

PRUDENTIAL SECURITIES INCORPORATED (an indirect wholly-owned subsidiary of the
Prudential Insurance Company of America)
One New York Plaza
New York, NY 10292
PAINEWEBBER INCORPORATED (a wholly-owned subsidiary of PaineWebber Group Inc.)
1285 Avenue of the Americas,
New York, NY 10019

Each Sponsor is a Delaware corporation and it, or its predecessor, has acted as
sponsor to many unit investment trusts. As a registered broker-dealer each
Sponsor buys and sells securities (including investment company shares) for
others (including investment companies) and participates as an underwriter in
various selling groups.

TRUSTEE

The Chase Manhattan Bank, Unit Investment Trust Department, 4 New York
Plaza--6th Floor, New York, New York 10004, is the Trustee.

It is supervised by the Federal Deposit Insurance Corporation, the Board of
Governors of the Federal Reserve System and New York State banking authorities.

UNDERWRITERS' AND SPONSORS' PROFITS

Underwriters receive sales charges when they sell units. The Sponsors also
realized a profit or loss on the initial deposit of the bonds. Any cash made
available by you to the Sponsors before the settlement date for those units may
be used in the Sponsors' businesses to the extent permitted by federal law and
may benefit the Sponsors.

A Sponsor or Underwriter may realize profits or sustain losses on bonds in the
Fund which were acquired from underwriting syndicates of which it was a member.

In maintaining a secondary market, the Sponsors will also realize profits or
sustain losses in the amount of any difference between the prices at which they
buy units and the prices at which they resell or redeem them.

                                       14
<PAGE>
PUBLIC DISTRIBUTION

The Sponsors do not intend to qualify units for sale in any foreign countries.
This prospectus does not constitute an offer to sell units in any country where
units cannot lawfully be sold.

CODE OF ETHICS

Merrill Lynch, as agent for the Sponsors, has adopted a code of ethics requiring
preclearance and reporting of personal securities transactions by its employees
with access to information on portfolio transactions. The goal of the code is to
prevent fraud, deception or misconduct against the Fund and to provide
reasonable standards of conduct.

YEAR 2000 ISSUES

Many computer systems were designed in such a way that they may be unable to
distinguish between the year 2000 and the year 1900 (commonly known as the 'Year
2000 Problem'). We do not expect that the computer system changes necessary to
prepare for the Year 2000 will cause any major operational difficulties for the
Fund. The Year 2000 Problem may adversely affect the issuers of the bonds
contained in the Portfolio, but we cannot predict whether any impact will be
material to the Fund as a whole.

TAXES

The following summary describes some of the important income tax consequences of
holding units. It assumes that you are not a dealer, financial institution,
insurance company or other investor with special circumstances. You should
consult your own tax adviser about your particular circumstances.

At the date of issue of each bond, counsel for the issuer delivered an opinion
to the effect that interest on the bond is exempt from regular federal income
tax. However, interest may be subject to state and local taxes and federal
alternative minimum tax. Neither we nor our counsel have reviewed the issuance
of the bonds, related proceedings or the basis for the opinions of counsel for
the issuers. We cannot assure you that the issuer (or other users) have complied
or will comply with any requirements necessary for a bond to be tax-exempt. If
any of the bonds were determined not to be tax-exempt, you could be required to
pay income tax for current and prior years, and if the Fund were to sell the
bond, it might have to sell it at a substantial discount.

In the opinion of our counsel, under existing law:

GENERAL TREATMENT OF THE FUND AND YOUR INVESTMENT

The Fund will not be taxed as a corporation for federal income tax purposes, and
you will be considered to own directly your share of each bond in the Fund.

GAIN OR LOSS UPON DISPOSITION

When all or part of your share of a bond is disposed of (for example, when the
Fund sells, exchanges or redeems a bond or when you sell or exchange your
units), you will generally recognize capital gain or loss. Your gain, however,
will generally be ordinary income to the extent of any accrued 'market
discount'. Generally you will have market discount to the extent that your basis
in a bond when you

                                       15
<PAGE>
purchase a unit is less than its stated redemption price at maturity (or, if it
is an original issue discount bond, the issue price increased by original issue
discount that has accrued on the bond before your purchase). You should consult
your tax adviser in this regard.

If your net long-term capital gains exceed your net short-term capital losses,
the excess may be subject to tax at a lower rate than ordinary income. Any
capital gain from the Fund will be long-term if you are considered to have held
your investment on each bond for more than one year and short-term otherwise. If
you are an individual and sell your units after holding them for more than one
year, you may be entitled to a 20% maximum federal tax rate on any resulting
gains. Consult your tax adviser in this regard. Because the deductibility of
capital losses is subject to limitations, you may not be able to deduct all of
your capital losses.

YOUR BASIS IN THE BONDS

Your aggregate basis in the bonds will be equal to the cost of your units,
including any sales charges and the organizational expenses you pay, adjusted to
reflect any accruals of 'original issue discount,' 'acquisition premium' and
'bond premium'. You should consult your tax adviser in this regard.

EXPENSES

If you are not a corporate investor, you will not be entitled to a deduction for
your share of fees and expenses of the Fund. Also, if you borrowed money in
order to purchase or carry your units, you will not be able to deduct the
interest on this borrowing for federal income tax purposes. The IRS may treat
your purchase of units as made with borrowed money even if the money is not
directly traceable to the purchase of units.

STATE AND LOCAL TAXES

Under the income tax laws of the State and City of New York, the Fund will not
be taxed as a corporation. If you are a New York taxpayer, your income from the
Fund will not be tax-exempt in New York except to the extent that the income is
earned on bonds that are tax-exempt for New York purposes. Depending on where
you live, your income from the Fund may be subject to state and local taxation.
You should consult your tax adviser in this regard.

SUPPLEMENTAL INFORMATION

You can receive at no cost supplemental information about the Fund by calling
the Trustee. The supplemental information includes more detailed risk disclosure
about the types of bonds that may be in the Fund's portfolio, general risk
disclosure concerning any insurance securing certain bonds, and general
information about the structure and operation of the Fund. The supplemental
information is also available from the SEC.

                                       16
<PAGE>
          MUNICIPAL INVESTMENT TRUST FUND,
          AMT MONTHLY PAYMENT SERIES - 100,
          DEFINED ASSET FUNDS

          REPORT OF INDEPENDENT ACCOUNTANTS

          The Sponsors, Trustee and Holders
          of Municipal Investment Trust Fund,
          AMT Monthly Payment Series - 100,
          Defined Asset Funds:

          We have audited the accompanying statement of condition of
          Municipal Investment Trust Fund, AMT Monthly Payment
          Series - 100, Defined Asset Funds, including the portfolio,
          as of July 31, 1999 and the related statements of
          operations and of changes in net assets for the year ended
          July 31, 1999 and the period August 9, 1997 to July 31, 1998.
          These financial statements are the responsibility of the
          Trustee. Our responsibility is to express an opinion on these
          financial statements based on our audits.

          We conducted our audits in accordance with generally
          accepted auditing standards. Those standards require that
          we plan and perform the audit to obtain reasonable
          assurance about whether the financial statements are free
          of material misstatement. An audit includes examining, on a
          test basis, evidence supporting the amounts and disclosures
          in the financial statements. Securities owned at July 31,
          1999, as shown in such portfolio, were confirmed to us by
          The Chase Manhattan Bank, the Trustee. An audit also includes
          assessing the accounting principles used and significant
          estimates made by the Trustee, as well as evaluating the
          overall financial statement presentation. We believe that our
          audits provide a reasonable basis for our opinion.

          In our opinion, the financial statements referred to
          above present fairly, in all material respects, the
          financial position of Municipal Investment Trust Fund, AMT
          Monthly Payment Series - 100, Defined Asset Funds at July
          31, 1999 and the results of its operations and changes in its
          net assets for the above-stated periods in conformity with
          generally accepted accounting principles.


          DELOITTE & TOUCHE LLP

          New York, N.Y.
          October 25, 1999


                                         D - 1.
<PAGE>
     MUNICIPAL INVESTMENT TRUST FUND,
     AMT MONTHLY PAYMENT SERIES - 100,
     DEFINED ASSET FUNDS


     STATEMENT OF CONDITION
     As of July 31, 1999

<TABLE>
     <S>                                                                                <C>             <C>
     TRUST PROPERTY:
       Investment in marketable securities -
{ 20}     at value (cost $ 6,730,015 )(Note 1).........                                                 $ 6,705,277
{ 36}  Accrued interest ...............................                                                      48,305
       Accrued interest on Segregated Bonds (Note 5) ..                                                       3,045
       Income payments receivable .....................                                                       4,370
       Principal payments receivable ..................                                                       1,942
{ 34}  Cash - principal ...............................                                                     114,201
       Cash - income on Segregated Bonds ..............                                                      27,293
       Deferred organization costs (Note 6) ...........                                                       6,094
                                                                                                        -----------
{ 40}    Total trust property .........................                                                   6,910,527


     LESS LIABILITIES:
{ 50}  Income advance from Trustee.....................                                 $    29,668
       Principal payments payable (Segregated Bonds) ..                                       2,700
       Principal payments payable .....................                                      30,300
{143}  Accrued Sponsors' fees .........................                                       2,274
       Other liabilities (Note 6) .....................                                       6,094          71,036
                                                                                        -----------     -----------


     NET ASSETS, REPRESENTED BY:
{ 80}  7,689 units of fractional undivided
{ 80}     interest outstanding (Note 3)................                                   6,818,758

{105}  Undistributed net investment income ............                                      20,733     $ 6,839,491
                                                                                        -----------     ===========

{130}UNIT VALUE ($ 6,839,491 / 7,689 units )...........                                                 $    889.52
                                                                                                        ===========


</TABLE>


                         See Notes to Financial Statements.


                                             D - 2.
<PAGE>
     MUNICIPAL INVESTMENT TRUST FUND,
     AMT MONTHLY PAYMENT SERIES - 100,
     DEFINED ASSET FUNDS


     STATEMENTS OF OPERATIONS
<TABLE>
<CAPTION>
                                                                                                       August 9, 1997
                                                                                       Year Ended            to
                                                                                        July 31,          July 31,
                                                                                          1999              1998
                                                                                          ----              ----

     <S>                                                                              <C>               <C>
     INVESTMENT INCOME:
{ 10}  Interest income ........................                                       $   444,864       $   525,327
       Interest income on Segregated
         Bonds (Note 5) .......................                                            13,305            17,034
{ 20}  Trustee's fees and expenses ............                                           (10,874)           (6,455)
{ 30}  Sponsors' fees .........................                                            (4,168)           (4,545)
                                                                                      ------------------------------
{ 40}  Net investment income ..................                                           443,127           531,361
                                                                                      ------------------------------


     REALIZED AND UNREALIZED GAIN (LOSS)
       ON INVESTMENTS:
       Realized gain (loss) on
{ 50}    securities sold or redeemed ..........                                            (4,823)            1,736
       Unrealized appreciation (depreciation)
{ 60}    of investments .......................                                          (242,137)          217,399
                                                                                      ------------------------------
       Net realized and unrealized
{ 70}     gain (loss) on investments ..........                                          (246,960)          219,135
                                                                                      ------------------------------


     NET INCREASE IN NET ASSETS
{ 80}  RESULTING FROM OPERATIONS ..............                                       $   196,167       $   750,496
                                                                                      ==============================


</TABLE>


                    See Notes to Financial Statements.


                                                     D - 3.
<PAGE>
     MUNICIPAL INVESTMENT TRUST FUND,
     AMT MONTHLY PAYMENT SERIES - 100,
     DEFINED ASSET FUNDS


     STATEMENTS OF CHANGES IN NET ASSETS
<TABLE>
<CAPTION>
                                                                                                      August 9, 1997
                                                                                       Year Ended            to
                                                                                        July 31,          July 31,
                                                                                          1999              1998
                                                                                          ----              ----

     <S>                                                                              <C>               <C>
     OPERATIONS:
{ 10}  Net investment income ..................                                       $   443,127       $   531,361
       Realized gain (loss) on
{ 20}    securities sold or redeemed ..........                                            (4,823)            1,736
       Unrealized appreciation (depreciation)
{ 30}    of investments .......................                                          (242,137)          217,399
                                                                                      ------------------------------
       Net increase in net assets
{ 40}    resulting from operations ............                                           196,167           750,496
                                                                                      ------------------------------

     DISTRIBUTIONS TO HOLDERS (Note 2):
{ 50}   Income ................................                                          (434,004)         (482,608)
        Principal .............................                                          (900,270)
                                                                                      ------------------------------
        Total distributions ...................                                        (1,334,274)         (482,608)
                                                                                      ------------------------------
     SHARE TRANSACTIONS:
       Deferred sales charge (Note 5):
         Income ...............................                                                              (4,001)
         Principal ............................                                          (171,124)         (134,847)

{ 82}  Redemption amounts:
         Income ...............................                                            (4,101)           (2,703)
{ 83}    Principal ............................                                        (1,630,130)         (758,128)
                                                                                      ------------------------------
{ 84}  Net share transactions .................                                        (1,805,355)         (899,679)
                                                                                      ------------------------------

{ 90}NET DECREASE IN NET ASSETS ...............                                        (2,943,462)          (631,791)

{100}NET ASSETS AT BEGINNING OF PERIOD ........                                         9,782,953         10,414,744
                                                                                      ------------------------------
{110}NET ASSETS AT END OF PERIOD ..............                                       $ 6,839,491       $  9,782,953
                                                                                      ==============================
     PER UNIT:
       Income distributions during
{120}    period ...............................                                       $     51.05       $     48.97
                                                                                      ==============================
       Principal distributions during
         period ...............................                                       $    110.59
                                                                                      ===========
       Net asset value at end of
{140}    period ...............................                                       $    889.52       $  1,047.20
                                                                                      ==============================
     TRUST UNITS:
{ 83}  Redeemed during period .................                                             1,653               750
{150}  Outstanding at end of period ...........                                             7,689             9,342
                                                                                      ==============================
</TABLE>
                         See Notes to Financial Statements.

                                   D - 4.
<PAGE>
MUNICIPAL INVESTMENT TRUST FUND,
AMT MONTHLY PAYMENT SERIES - 100,
DEFINED ASSET FUNDS

NOTES TO FINANCIAL STATEMENTS

1. SIGNIFICANT ACCOUNTING POLICIES

The Fund is registered under the Investment Company Act of 1940 as a Unit
Investment Trust. The following is a summary of significant accounting
policies consistently followed by the Fund in the preparation of its
financial statements. The policies are in conformity with generally accepted
accounting principles.

(A) Securities are stated at value as determined by the
Evaluator based on bid side evaluations for the securities,
except that value on August 9, 1997 was based upon offering
side evaluations at August 7, 1997, the day prior to the
Date of Deposit. Cost of securities at August 9, 1997 was
also based on such offering side evaluations.

(B) The Fund is not subject to income taxes. Accordingly, no
provision for such taxes is required.

(C) Interest income is recorded as earned.

2. DISTRIBUTIONS

A distribution of net investment income is made to Holders each month.
Receipts other than interest, after deductions for redemptions and applicable
expenses, are also distributed periodically.

     3.   NET CAPITAL
<TABLE>
     <S>                                                                                                <C>
{ 10}     Cost of 7,689 units at Date of Deposit .....................                                  $ 7,934,896
          Transfer of capital to interest on Segregated Bonds (Note 5)                                       30,339
{ 31}     Redemptions of units - net cost of 2,403 units redeemed
{143}       less redemption amounts (principal).......................                                       91,590
          Principal distributions ....................................                                     (900,270)
          Deferred sales charge (Note 5) .............................                                     (309,972)
{ 40}     Realized loss on securities sold or redeemed ...............                                       (3,087)
{ 70}     Net unrealized depreciation of investments..................                                      (24,738)
                                                                                                        -----------

{ 80}     Net capital applicable to Holders ..........................                                  $ 6,818,758
                                                                                                        ===========
</TABLE>
4. INCOME TAXES

As of July 31, 1999, net unrealized depreciation of investments, based on cost
for Federal income tax purposes, aggregated $24,738, of which $62,754 related
to depreciated securities and $38,016 related to appreciated securities. The
cost of investment securities for Federal income tax purposes was $6,730,015
at July 31, 1999.


                                    D - 5.
<PAGE>
MUNICIPAL INVESTMENT TRUST FUND,
AMT MONTHLY PAYMENT SERIES - 100,
DEFINED ASSET FUNDS

NOTES TO FINANCIAL STATEMENTS


5. DEFERRED SALES CHARGE

$120,000 face amount of the Town of Brookhaven, Suffolk Cnty., NY, Pub. Imp.
Serial Bonds 1997 and $60,000 face amount of Harris Cnty., TX, Hlth. Facs. Dev.
Corp., Hosp. Rev. Bonds, Ser. 1997 A have been segregated to fund the deferred
sales charges. The sales charges are being paid for with the interest received
and by periodic sales or maturity of these bonds. A deferred sales charge of
$3.75 per Unit is charged on a quarterly basis, and paid to the Sponsors
periodically by the Trustee on behalf of the Holders, up to an aggregate of
$45 per Unit over the first three years of the life of the Fund. Should a Holder
redeem Units prior to the third anniversary of the Fund, the remaining balance
of the deferred sales charge will be charged.

6. DEFERRED ORGANIZATION COSTS

Deferred organization costs are being amortized over five years. Included in
"Other liabilities" on the Statement of Condition is $6,094 payable to the
Trustee for reimbursement of costs related to the organization of the Trust.
































                               D - 6.
<PAGE>
     MUNICIPAL INVESTMENT TRUST FUND,
     AMT MONTHLY PAYMENT SERIES - 100,
     DEFINED ASSET FUNDS

     PORTFOLIO
     As of July 31, 1999

<TABLE>
<CAPTION>

                                               Rating                                            Optional
     Portfolio No. and Title of                  of         Face                                 Redemption
            Securities                       Issues(1)      Amount    Coupon      Maturities(3) Provisions(3)    Cost(2)   Value(2)
            ----------                       ---------  ----------- -----------   ------------  ------------  ----------  ---------
<S>                                          <C>        <C>         <C>           <C>          <C>          <C>         <C>

   1 Iowa Fin. Auth., Single Family Mtge.       AAA     $   990,000     5.850 %      2028      07/01/07     $   990,000 $ 1,007,078
     Bonds, Ser. 1997 H (AMT) (5)                            {46246LHW3  }                     @  102.000

   2 City of Chicago, IL, Chicago Midway        AAA         375,000     5.625        2029      01/01/07         377,329     373,643
     Airport Rev. Bonds, Ser. 1996 B (AMT)                   {167562CC9  }                     @  101.000
     (MBIA Ins. ) (4) (5)

   3 Louisiana Hsg. Fin. Agy., Single Family    Aaa(m)      845,000     5.750        2028      06/01/07         845,000     851,870
     Mtge. Rev. Bonds, Ser. 1997 B-2 (AMT)                   {546265W39  }                     @  102.000
     (5)

   4 New Mexico Mtge. Fin. Auth., Single        AAA         940,000     5.750        2029      07/01/07         940,000     947,727
     Family Mtge. Prog. Bonds, Ser. 1997 E-2                 {647199BE7  }                     @  102.000
     (AMT) (5)

   5 New York State Urban Dev. Corp., Corr.     BBB+        380,000     5.375        2025      01/01/06         368,068     363,998
     Cap. Fac. Rev. Bonds, Ser. 6                            {6500336S7  }                     @  102.000

   6 Dormitory Auth. of the State of New        A-          540,000     5.500        2026      05/15/06         536,090     527,380
     York, State Univ. Educl. Fac., Rev.                     {649836MR1  }                     @  102.000
     Bonds, Ser. 1996

   7 Town of Brookhaven, Suffolk Cnty., NY,     Aaa(m)      120,000     4.600        2000      None             122,029     121,283
     Pub. Imp. Serial Bonds 1997 (MBIA Ins.)                 {1131515Y6  }
     (4) (6)

   8 Harris Cnty., TX, Hlth. Facs. Dev.         AAA          60,000     5.000        2000      None              61,179      60,671
     Corp., Hosp. Rev. Bonds (Memorial Hosp.                 {414152LX4  }
     Sys. Proj.), Ser. 1997 A (MBIA Ins.)
     (4) (6)

   9 Murray City, UT, Hosp. Rev. Bonds (IHC     AAA       1,000,000     4.750        2020      05/15/06         915,320     886,170
     Hlth. Svcs., Inc.), Ser. 1996 (MBIA                     {626853BX2  }                     @  100.000
     Ins.) (4)




</TABLE>
                                                      D - 7.
<PAGE>

     MUNICIPAL INVESTMENT TRUST FUND,
     AMT MONTHLY PAYMENT SERIES - 100,
     DEFINED ASSET FUNDS

     PORTFOLIO
     As of July 31, 1999

<TABLE>
<CAPTION>

                                               Rating                                            Optional
     Portfolio No. and Title of                  of         Face                                 Redemption
            Securities                       Issues(1)      Amount    Coupon      Maturities(3) Provisions(3)    Cost(2)   Value(2)
            ----------                       ---------  ----------- -----------   ------------  ------------  ----------  ---------
<S>                                          <C>        <C>         <C>           <C>          <C>          <C>         <C>

  10 Virginia Port. Auth., Port. Fac. Rev.      AAA     $   795,000     5.500 %      2024      07/01/07     $   795,000 $   779,116
     Bonds, Ser. 1997 (MBIA Ins.) (AMT) (4)                  {928077CW4  }                     @  101.000
     (5)

  11 Washington State Hsg. Fin. Comm.,          Aaa(m)      780,000     5.750        2028      06/01/07         780,000     786,341
     Single Family Prog. Bonds, Ser. 1997 3A                 {93978KJY5  }                     @  101.500
     (AMT) (5)

                                                          ---------                                           ---------   ---------
     TOTAL                                              $ 6,825,000                                         $ 6,730,015 $ 6,705,277
                                                          =========                                           =========   =========

                                        See Notes to Portfolio.
</TABLE>


                                                   D - 8.
<PAGE>
MUNICIPAL INVESTMENT TRUST FUND,
AMT MONTHLY PAYMENT SERIES - 100,
DEFINED ASSET FUNDS

NOTES TO PORTFOLIO
As of July 31, 1999

(1) The ratings of the bonds are by Standard & Poor's Ratings Group, or by
Moody's Investors Service, Inc if followed by "(m)", or by Fitch Investors
Service, Inc if followed by "(f)"; "NR" indicates that this bond is not
currently rated by any of the above mentioned rating services. These ratings
have been furnished by the Evaluator but not confirmed with the rating
agencies.

(2) See Notes to Financial Statements.

(3) Optional redemption provisions, which may be exercised in whole or in part,
are initially at prices of par plus a premium, then subsequently at prices
declining to par. Certain securities may provide for redemption at par prior
or in addition to any optional or mandatory redemption dates or maturity, for
example, through the operation of a maintenance and replacement fund, if
proceeds are not able to be used as contemplated, the project is condemned or
sold or the project is destroyed and insurance proceeds are used to redeem
the securities. Many of the securities are also subject to mandatory sinking
fund redemption commencing on dates which may be prior to the date on which
securities may be optionally redeemed. Sinking fund redemptions are at par
and redeem only part of the issue. Some of the securities have mandatory
sinking funds which contain optional provisions permitting the issuer to
increase the principal amount of securities called on a mandatory redemption
date. The sinking fund redemptions with optional provisions may, and optional
refunding redemptions generally will, occur at times when the redeemed
securities have an offering side evaluation which represents a premium over
par. To the extent that the securities were acquired at a price higher than
the redemption price, this will represent a loss of capital when compared
with the Public Offering Price of the Units when acquired. Distributions will
generally be reduced by the amount of the income which would otherwise have
been paid with respect to redeemed securities and there will be distributed
to Holders any principal amount and premium received on such redemption after
satisfying any redemption requests for Units received by the Fund. The
estimated current return may be affected by redemptions.

(4) Insured by the indicated municipal bond insurance company.

(5) Securities that are tax preference items for purposes of the Alternative
Minimum Tax are indicated by "(AMT)".

(6) These bonds have been segregated to fund the deferred sales charges.


                   D - 9.





<PAGE>
                             Defined
                             Asset FundsSM


HAVE QUESTIONS ?                         MUNICIPAL INVESTMENT TRUST FUND
Request the most recent free             AMT MONTHLY PAYMENT SERIES--100
Information Supplement                   (A Unit Investment Trust)
that gives more details about            ---------------------------------------
the Fund, by calling:                    This Prospectus does not contain
The Chase Manhattan Bank                 complete information about the
1-800-323-1508                           investment company filed with the
                                         Securities and Exchange Commission in
                                         Washington, D.C. under the:
                                         o Securities Act of 1933 (file no.
                                         33-48867) and
                                         o Investment Company Act of 1940 (file
                                         no. 811-1777).
                                         TO OBTAIN COPIES AT PRESCRIBED RATES--
                                         WRITE: Public Reference Section of the
                                         Commission
                                         450 Fifth Street, N.W., Washington,
                                         D.C. 20549-6009
                                         CALL: 1-800-SEC-0330.
                                         VISIT: http://www.sec.gov.
                                         ---------------------------------------
                                         No person is authorized to give any
                                         information or representations about
                                         this Fund not contained in this
                                         Prospectus or the Information
                                         Supplement, and you should not rely on
                                         any other information.
                                         ---------------------------------------
                                         When units of this Fund are no longer
                                         available, this Prospectus may be used
                                         as a preliminary prospectus for a
                                         future series, but some of the
                                         information in this Prospectus will be
                                         changed for that series.
                                         Units of any future series may not be
                                         sold nor may offers to buy be accepted
                                         until that series has become effective
                                         with the Securities and Exchange
                                         Commission. No units can be sold in any
                                         State where a sale would be illegal.


                                                     11312--11/99
<PAGE>
                        MUNICIPAL INVESTMENT TRUST FUND
                           AMT MONTHLY PAYMENT SERIES
                              DEFINED ASSET FUNDS
                       CONTENTS OF REGISTRATION STATEMENT

     This Post-Effective Amendment to the Registration Statement on Form S-6
comprises the following papers and documents:

     The facing sheet of Form S-6.

     The cross-reference sheet (incorporated by reference to the Cross-Reference
Sheet to the Registration Statement of Defined Asset Funds Municipal Insured
Series, 1933 Act File No. 33-54565).

     The Prospectus.

     The Signatures.

The following exhibits:

     1.1.1--Form of Standard Terms and Conditions of Trust Effective as of
            October 21, 1993 (incorporated by reference to Exhibit 1.1.1 to the
            Registration Statement of Municipal Investment Trust Fund,
            Multi-state Series--48, 1933 Act File No. 33-50247).

     4.1  --Consent of the Evaluator.

     5.1  --Consent of independent accountants.

     9.1  --Information Supplement (incorporated by reference to Exhibit 9.1 to
            Amendment No. 4 to the Registration Statement of Municipal
            Investment Trust Fund, Multistate Series--409, 1933 Act File No.
         333-81777).

                                      R-1
<PAGE>
                        MUNICIPAL INVESTMENT TRUST FUND
                        AMT MONTHLY PAYMENT SERIES--100
                              DEFINED ASSET FUNDS

                                   SIGNATURES

     PURSUANT TO THE REQUIREMENTS OF THE SECURITIES ACT OF 1933, THE REGISTRANT,
MUNICIPAL INVESTMENT TRUST FUND, AMT MONTHLY PAYMENT SERIES--100, DEFINED ASSET
FUNDS CERTIFIES THAT IT MEETS ALL OF THE REQUIREMENTS FOR EFFECTIVENESS OF THIS
REGISTRATION STATEMENT PURSUANT TO RULE 485(B) UNDER THE SECURITIES ACT OF 1933
AND HAS DULY CAUSED THIS REGISTRATION STATEMENT OR AMENDMENT TO THE REGISTRATION
STATEMENT TO BE SIGNED ON ITS BEHALF BY THE UNDERSIGNED THEREUNTO DULY
AUTHORIZED IN THE CITY OF NEW YORK AND STATE OF NEW YORK ON THE 29TH DAY OF
NOVEMBER, 1999.

             SIGNATURES APPEAR ON PAGES R-3, R-4, R-5, R-6 AND R-7.

     A majority of the members of the Board of Directors of Merrill Lynch,
Pierce, Fenner & Smith Incorporated has signed this Registration Statement or
Amendment to the Registration Statement pursuant to Powers of Attorney
authorizing the person signing this Registration Statement or Amendment to the
Registration Statement to do so on behalf of such members.

     A majority of the members of the Board of Directors of Salomon Smith Barney
Inc. has signed this Registration Statement or Amendment to the Registration
Statement pursuant to Powers of Attorney authorizing the person signing this
Registration Statement or Amendment to the Registration Statement to do so on
behalf of such members.

     A majority of the members of the Board of Directors of Prudential
Securities Incorporated has signed this Registration Statement or Amendment to
the Registration Statement pursuant to Powers of Attorney authorizing the person
signing this Registration Statement or Amendment to the Registration Statement
to do so on behalf of such members.

     A majority of the members of the Executive Committee of the Board of
Directors of PaineWebber Incorporated has signed this Registration Statement or
Amendment to the Registration Statement pursuant to Powers of Attorney
authorizing the person signing this Registration Statement or Amendment to the
Registration Statement to do so on behalf of such members.

     A majority of the members of the Board of Directors of Dean Witter Reynolds
Inc. has signed this Registration Statement or Amendment to the Registration
Statement pursuant to Powers of Attorney authorizing the person signing this
Registration Statement or Amendment to the Registration Statement to do so on
behalf of such members.

                                      R-2
<PAGE>
               MERRILL LYNCH, PIERCE, FENNER & SMITH INCORPORATED
                                   DEPOSITOR


By the following persons, who constitute  Powers of Attorney have been filed
  a majority of                             under
  the Board of Directors of Merrill         Form SE and the following 1933 Act
  Lynch, Pierce,                            File
  Fenner & Smith Incorporated:              Number: 333-70593


      GEORGE A. SCHIERIN
      JOHN L. STEFFENS
      By J. DAVID MEGLEN
       (As authorized signatory for Merrill Lynch, Pierce,
       Fenner & Smith Incorporated and
       Attorney-in-fact for the persons listed above)

                                      R-3
<PAGE>
                           SALOMON SMITH BARNEY INC.
                                   DEPOSITOR


By the following persons, who constitute a majority of      Powers of Attorney
  the Board of Directors of Salomon Smith Barney Inc.:        have been filed
                                                              under the 1933 Act
                                                              File Numbers:
                                                              333-63417 and
                                                              333-63033


      MICHAEL A. CARPENTER
      DERYCK C. MAUGHAN

      By GINA LEMON
       (As authorized signatory for
       Salomon Smith Barney Inc. and
       Attorney-in-fact for the persons listed above)

                                      R-4
<PAGE>
                       PRUDENTIAL SECURITIES INCORPORATED
                                   DEPOSITOR


By the following persons, who constitute a majority of      Powers of Attorney
  the Board of Directors of Prudential Securities             have been filed
  Incorporated:                                               under Form SE and
                                                              the following 1933
                                                              Act File Numbers:
                                                              33-41631 and
                                                              333-15919


      ROBERT C. GOLDEN
      ALAN D. HOGAN
      A. LAURENCE NORTON, JR.
      LELAND B. PATON
      VINCENT T. PICA II
      MARTIN PFINSGRAFF
      HARDWICK SIMMONS
      LEE B. SPENCER, JR.
      BRIAN M. STORMS

      By RICHARD R. HOFFMANN
       (As authorized signatory for Prudential Securities
       Incorporated and Attorney-in-fact for the persons
       listed above)

                                      R-5
<PAGE>
                            PAINEWEBBER INCORPORATED
                                   DEPOSITOR


By the following persons, who constitute  Powers of Attorney have been filed
  the Board of Directors of PaineWebber     under
  Incorporated:                             the following 1933 Act File
                                            Number: 33-55073


      MARGO N. ALEXANDER
      TERRY L. ATKINSON
      BRIAN M. BAREFOOT
      STEVEN P. BAUM
      MICHAEL CULP
      REGINA A. DOLAN
      JOSEPH J. GRANO, JR.
      EDWARD M. KERSCHNER
      JAMES P. MacGILVRAY
      DONALD B. MARRON
      ROBERT H. SILVER
      MARK B. SUTTON
      By
       ROBERT E. HOLLEY
       (As authorized signatory for
       PaineWebber Incorporated
       and Attorney-in-fact for the persons listed above)

                                      R-6
<PAGE>
                           DEAN WITTER REYNOLDS INC.
                                   DEPOSITOR


By the following persons, who constitute  Powers of Attorney have been filed
  a majority of                             under Form SE and the following 1933
  the Board of Directors of Dean Witter     Act File Numbers: 33-17085,
  Reynolds Inc.:                            333-13039 and 333-47553


      RICHARD M. DeMARTINI
      RAYMOND J. DROP
      JAMES F. HIGGINS
      MITCHELL M. MERIN
      STEPHEN R. MILLER
      PHILIP J. PURCELL
      THOMAS C. SCHNEIDER
      By
       MICHAEL D. BROWNE
       (As authorized signatory for
       Dean Witter Reynolds Inc.
       and Attorney-in-fact for the persons listed above)

                                      R-7

<PAGE>
                                                                     EXHIBIT 4.1

                               STANDARD & POOR'S
                    A DIVISION OF THE McGRAW-HILL COMPANIES
                                  J. J. KENNY
                                  65 BROADWAY
                           NEW YORK, N.Y. 10006-2551
                            TELEPHONE (212) 770-4422
                                FAX 212/797-8681

                                                   November 29, 1999

Frank A. Ciccotto, Jr.
Vice President
Tax-Exempt Evaluations


Merrill Lynch, Pierce, Fenner & Smith
Incorporated
Defined Asset Funds
P.O. Box 9051
Princeton, New Jersey 08543-9051
The Chase Manhattan Bank
4 New York Plaza, 6th Floor
New York, New York 10004


RE: MUNICIPAL INVESTMENT TRUST FUND,
     AMT MONTHLY PAYMENT SERIES--100, DEFINED ASSET FUNDS

Gentlemen:

     We have examined the post-effective Amendment to the Registration Statement
File No. 33-48867 for the above-captioned trust. We hereby acknowledge that
Kenny S&P Evaluation Services, a division of J. J. Kenny Co., Inc. is currently
acting as the evaluator for the trust. We hereby consent to the use in the
Amendment of the reference to Kenny S&P Evaluation Services, a division of J. J.
Kenny Co., Inc. as evaluator.

     In addition, we hereby confirm that the ratings indicated in the
above-referenced Amendment to the Registration Statement for the respective
bonds comprising the trust portfolio are the ratings currently indicated in our
KENNYBASE database.

     You are hereby authorized to file copies of this letter with the Securities
and Exchange Commission.

                                                   Sincerely,
                                                   FRANK A. CICCOTTO
                                                   Vice President

<PAGE>
                                                                     Exhibit 5.1
                       CONSENT OF INDEPENDENT ACCOUNTANTS
The Sponsors and Trustee of
Municipal Investment Trust Fund--AMT Monthly Payment Series--100, Defined Asset
Funds

We consent to the use in this Post-Effective Amendment No. 2 to Registration
Statement No. 33-48867 of our opinion dated October 25, 1999 appearing in the
Prospectus, which is part of such Registration Statement, and to the reference
to us under the heading 'Auditors' in such Prospectus.

DELOITTE & TOUCHE LLP
New York, N.Y.
November 29, 1999


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