ATMI INC, S-3/A, 2000-03-16

ATMI INC
S-3/A, 2000-03-16
INDUSTRIAL INORGANIC CHEMICALS

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<PAGE>

As filed with the Securities and Exchange Commission on March 16, 2000

Registration No. 333-31982
- --------------------------------------------------------------------------------
- --------------------------------------------------------------------------------
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549

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AMENDMENT NO. 1

TO
FORM S-3
REGISTRATION STATEMENT
UNDER
THE SECURITIES ACT OF 1933

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ATMI, INC.
(Exact name of registrant as specified in its charter)
Delaware 06-1481060
(State or other jurisdiction of (I.R.S. Employer
incorporation or organization) Identification No.)

7 Commerce Drive
Danbury, Connecticut 06810
(203) 794-1100
(Address, including zip code, and telephone number, including area code, of
registrant's principal executive offices)

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Eugene G. Banucci, Ph.D.
Chief Executive Officer
ATMI, Inc.
7 Commerce Drive
Danbury, Connecticut 06810
(203) 794-1100
(Name, address, including zip code, and telephone number, including area code,
of agent for service)

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

Copies to:

Donna L. Brooks, Esq. Keith F. Higgins, Esq.
Shipman & Goodwin LLP Ann L. Milner, Esq.
One American Row Ropes & Gray
Hartford, Connecticut 06103 One International Place
Telephone No.: (860) 251-5000 Boston, Massachusetts 02110
Facsimile No.: (860) 251-5999 Telephone No.: (617) 951-7000
Facsimile No.: (617) 951-7050

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Approximate date of commencement of proposed sale to the public: As soon as
practicable after the effective date of this Registration Statement.
If the only securities being registered on this Form are being offered
pursuant to dividend or interest reinvestment plans, please check the following
box. [_]
If any of the securities being registered on this Form are to be offered on
a delayed or continuous basis pursuant to Rule 415 under the Securities Act of
1933, other than securities offered only in connection with dividend or
interest reinvestment plans, check the following box. [_]
If this Form is filed to register additional securities for an offering
pursuant to Rule 462(b) under the Securities Act, please check the following
box and list the Securities Act registration statement number of the earlier
effective registration statement for the same offering. [_]
If this Form is a post-effective amendment filed pursuant to Rule 462(c)
under the Securities Act, check the following box and list the Securities Act
registration statement number of the earlier effective registration statement
for the same offering. [_]
If delivery of the prospectus is expected to be made pursuant to Rule 434,
please check the following box. [_]

--------------
The Registrant hereby amends this Registration Statement on such date or
dates as may be necessary to delay its effective date until the Registrant
shall file a further amendment which specifically states that this Registration
Statement shall thereafter become effective in accordance with Section 8(a) of
the Securities Act of 1933 or until this Registration Statement shall become
effective on such date as the Commission, acting pursuant to said Section 8(a),
may determine.

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<PAGE>

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+The information in this preliminary prospectus is not complete and may be +
+changed. These securities may not be sold until the registration statement +
+filed with the Securities and Exchange Commission is effective. This +
+preliminary prospectus is not an offer to sell nor does it seek an offer to +
+buy these securities in any jurisdiction where the offer or sale is not +
+permitted. +
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Subject To Completion. Dated March 13, 2000.

3,100,000 Shares

[LOGO] ATMI, INC.

Common Stock

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ATMI, Inc. is offering 1,500,000 of the shares to be sold in the offering.
The selling stockholders identified in this prospectus are offering an
additional 1,600,000 shares. ATMI will not receive any of the proceeds from the
sale of shares being sold by the selling stockholders.

The common stock is quoted on the Nasdaq National Market under the symbol
"ATMI". The last reported sale price of our common stock on March 10, 2000 was
$56.31 per share.

See "Risk Factors" beginning on page 6 to read about factors you should
consider before buying shares of our common stock.

-----------

Neither the Securities and Exchange Commission nor any other regulatory body
has approved or disapproved of these securities or passed upon the accuracy or
adequacy of this prospectus. Any representation to the contrary is a criminal
offense.

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<TABLE>
<CAPTION>
Per Share Total
--------- -----
<S> <C> <C>
Initial price to public......................................... $ $
Underwriting discount........................................... $ $
Proceeds, before expenses, to ATMI.............................. $ $
Proceeds, before expenses, to the selling stockholders.......... $ $
</TABLE>

To the extent that the underwriters sell more than 3,100,000 shares of common
stock, the underwriters have the option to purchase up to an additional 225,000
shares from ATMI and 240,000 shares from certain of the selling stockholders at
the initial price to the public less the underwriting discount.

-----------

The underwriters expect to deliver the shares against payment in New York,
New York on , 2000.

Goldman, Sachs & Co.
Banc of America Securities LLC
Deutsche Banc Alex. Brown
Prudential Volpe Technology
a unit of Prudential Securities

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Prospectus dated , 2000.
<PAGE>

PROSPECTUS SUMMARY

This summary highlights information contained elsewhere in this prospectus.
You should read this entire prospectus carefully. Unless otherwise indicated,
all information in this prospectus assumes that the underwriters will not
exercise their over-allotment option. This prospectus contains forward-looking
statements that involve risks, uncertainties and assumptions. The actual
results could differ materially from those anticipated in these forward-looking
statements as a result of certain factors, including but not limited to those
set forth under "Risk Factors" and elsewhere in this prospectus.

ATMI

We are a leading supplier of materials, equipment and related services used
worldwide in the manufacture of semiconductor devices. We specifically target
the "front-end" semiconductor materials market. This market includes the
processes used to convert a bare silicon wafer into a fully functional wafer
that contains many copies of a semiconductor device or "chip". To complete the
manufacturing process, this functional wafer is taken through a "back-end"
manufacturing process that includes wafer dicing into chips, packaging and
testing. Our customers include most of the leading semiconductor manufacturers
in the world, including Intel, Taiwan Semiconductor, Hyundai, Texas Instruments
and IBM.

We have further refined our market focus to target only specialty materials
used in front-end semiconductor manufacture. These specialty materials are used
in eight key process steps that are used repetitively to add functionality to a
silicon wafer. In recent years, the semiconductor industry has grown worldwide,
and front-end manufacturing processes have become increasingly complex,
resulting in rapidly changing requirements for semiconductor materials. We have
capitalized on the growth of the semiconductor industry in general, and front-
end processing in particular, through:

. a comprehensive research and development program that has provided a
stream of proprietary and patented products for this market;

. a strategy of delivering a complete materials solution to our customers
including materials, packaging, delivery systems, sensing and abatement;
and

. an aggressive mergers and acquisitions effort that has allowed us to more
rapidly move towards one-stop purchasing for our customers.

We have organized our operations along two business segments: ATMI
Materials and ATMI Technologies. ATMI Materials provides:

. a broad range of ultrahigh purity semiconductor materials; and

. semiconductor materials packaging and delivery systems;

ATMI Technologies provides:

. sensors for the workplace and environment that detect materials as they
move through the workplace;

. point-of-use environmental equipment that abates materials; and

. specialty thin film deposition services that provide coated wafers
directly to our customers.

We also conduct our venture activities and our government funded research
and development activities through ATMI Technologies.

3
<PAGE>

Over the last five years, we have achieved a leadership position by
providing a more complete line of products than our competitors through
innovation and acquisitions. We plan to continue our growth through product
line expansion in each of our existing market segments and to leverage our core
technology to create new high growth businesses.

Our principal executive offices are located at 7 Commerce Drive, Danbury,
Connecticut 06810, and our telephone number is (203) 794-1100. Our Internet
address is www.atmi.com. The information contained on our website is not
incorporated by reference in this prospectus. Unless the context otherwise
requires, references in this prospectus to "ATMI", "we", "us" and "our" refer
to ATMI, Inc. and our subsidiaries. This prospectus contains some of our
trademarks and trade names as well as trademarks and trade names of other
companies.

The Offering

<TABLE>
<S> <C>
Shares offered by ATMI......... 1,500,000 shares
Shares offered by selling
stockholders.................. 1,600,000 shares
Shares to be outstanding after
the offering.................. 29,542,250 shares
Nasdaq National Market symbol.. ATMI
Use of proceeds................ For general corporate purposes and working
capital, including potential acquisitions,
capital expenditures and research, development
and commercialization programs.
</TABLE>

The shares of common stock to be outstanding after the offering exclude
3,059,253 shares issuable upon the exercise of outstanding stock options and
warrants issued by us as of March 10, 2000 at a weighted average exercise price
of $21.64 per share.

4
<PAGE>

Summary Consolidated Financial Information
(in thousands, except per share data)

<TABLE>
<CAPTION>
Year Ended December 31,
--------------------------------------------------------
1995 1996 1997 1998 1999
----------- -------- -------- -------- --------
(unaudited)
<S> <C> <C> <C> <C> <C>
Consolidated Statement
of Income Data:
Revenues................ $115,984 $154,390 $192,012 $165,106 $196,236
Gross profit............ 59,204 80,717 99,451 81,687 103,266
Operating income........ 14,150 17,968(1) 15,522(3) 6,432(4) 14,688(5)(6)
Net income.............. $ 8,401 $ 13,093(2) $ 6,395 $ 4,935 $ 10,546
Net income per share--
assuming dilution...... $ 0.36 $ 0.54(2) $ 0.25 $ 0.18 $ 0.37
Weighted average shares
outstanding--assuming
dilution............... 23,051 24,318 25,660 27,423 28,319
</TABLE>

<TABLE>
<CAPTION>
December 31, 1999
--------------------
Actual As Adjusted
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(unaudited)
<S> <C> <C>
Consolidated Balance Sheet Data:
Cash, cash equivalents and marketable securities........... $ 92,174 $171,819
Working capital............................................ 121,199 200,844
Total assets............................................... 232,656 312,301
Long-term debt, less current portion....................... 6,280 6,280
Total stockholders' equity................................. 174,805 254,450
</TABLE>

The as adjusted column above reflects our sale of 1,500,000 shares of
common stock at an assumed public offering price of $56.31 per share, after
deducting the estimated underwriters' discounts and commissions and offering
expenses payable by us.
- --------
(1) Includes $2.0 million accrued in connection with patent litigation
involving Lawrence Semiconductor Laboratories (prior to our acquisition of
that company), which resulted in a settlement payment in May 1997.
(2) Net income and net income per share--assuming dilution in 1996 include the
effect of the treatment of our ADCS subsidiary as an S-Corporation for a
portion of 1996 (which was prior to our acquisition of ADCS). If ADCS had
been taxed as a C-Corporation for all of 1996, our net income and net
income per share--assuming dilution would have been approximately $11.6
million and $0.48, respectively, for the year ended December 31, 1996.
(3) Includes costs of $9.0 million incurred in investigating, analyzing and
completing our acquisitions of ADCS and Lawrence Semiconductor
Laboratories.

(4) lncludes costs of $1.7 million incurred in connection with the completion
of our acquisition of NOW Technologies.
(5) Includes $2.3 million for severance for several former executives within
ATMI Materials and ATMI Technologies.
(6) Includes $3.3 million incurred in connection with the completion of our
acquisitions of MST Analytics and Newform and $7.2 million incurred in
connection with our acquisitions of Delatech, ACSI and TeloSense offset by
a reversal of $0.6 million for previously accrued merger related costs.

5
<PAGE>

RISK FACTORS

You should carefully consider the following risks, together with other
information contained or incorporated by reference in this prospectus, before
making an investment decision. Any of the following risks could adversely
affect our business, operating results and financial condition. The trading
price of our common stock could decline due to any of these risks, and you
could lose all or part of your investment.

Our operating results are materially dependent upon economic and business
conditions in the semiconductor industry, and we are vulnerable to industry
downturns.

Substantially all of our sales are to customers in the worldwide
semiconductor industry. As a result, our operating results are materially
dependent upon economic and business conditions in the semiconductor industry.
The semiconductor industry and the semiconductor equipment industry in
particular have been highly cyclical and have experienced periods of
overcapacity at various times, resulting in significantly reduced demand for
semiconductor materials, capital equipment and wafer processing services. The
semiconductor industry experienced a significant downturn in 1998, which
resulted in a reduction in our revenues and earnings. Any future industry
downturn will likely have a similar impact. Although the semiconductor industry
is recovering from the 1998 downturn, we cannot assure you that:

. conditions in the semiconductor industry will continue to improve;

. the semiconductor industry will not experience other, possibly more
severe and prolonged, downturns in the future; or

. the current recovery will continue to result in increased demand for
semiconductor materials, capital equipment and wafer processing services
by the semiconductor industry.

The end of the current recovery or any future downturn in the semiconductor
industry will have a material adverse effect on our business, operating results
and financial condition.

Our quarterly operating results may fluctuate, and our stock price may be
volatile as a result.

Our quarterly operating results may fluctuate in the future as a result of
a number of factors, including:

. the general demand for semiconductors;

. the cyclical nature of the semiconductor manufacturing equipment market;

. our product mix;

. our success in developing, introducing and shipping new products;

. competition;

. the timing of significant orders from, and shipments to, customers;

. the timing and market acceptance of new products;

. seasonality of sales; and

. the effect of various non-recurring expenses.

As a result, our operating results in any quarter are not necessarily a good
predictor of our results for any future period. In the future, we will likely
experience quarterly or annual fluctuations. In one or more future quarters,
our operating results may fall below the expectations of public market analysts
or investors, and the price of our common stock could decline significantly.

6
<PAGE>

We may have difficulty managing our growth and attracting and retaining highly
skilled scientific, technical, managerial and marketing personnel, which could
adversely affect our revenues and increase our operating expenses.

We have grown and intend to continue to grow our business. The management
of our growth requires qualified personnel, systems and other resources. Our
future success will depend in part on our ability to attract and retain highly
skilled scientific, technical, managerial and marketing personnel. Competition
for such personnel in the semiconductor industry is intense, and our
competitors are often larger and more established than we are. We may not be
successful in attracting and retaining qualified personnel. In addition, our
expansion may also significantly strain operational, management, financial,
sales and marketing and other resources. To manage growth effectively, we must
continue to enhance our information technology infrastructure, systems and
controls and successfully expand, train and manage our employee base. We may
not be able to manage this expansion effectively, including providing
satisfactory levels of customer service and technical support.

Our business, operating results and financial condition could be negatively
impacted if we are unable to integrate businesses we acquire.

During the past three years, we have acquired several companies, including
Advanced Delivery and Chemical Systems, Lawrence Semiconductor Laboratories,
NOW Technologies, Delatech, Advanced Chemical Systems International, TeloSense,
Newform and MST Analytics. If opportunities exist, we intend to acquire other
businesses that we believe fit our business strategy. We may not achieve the
anticipated benefits from any acquisition, including the acquisitions listed
above, unless we successfully combine the acquired businesses with those of
ATMI in a timely and efficient manner. The integration of acquisitions requires
substantial attention from our management. The diversion of the attention of
management, and any difficulties encountered in the transition process, could
negatively impact our business, operating results and financial condition. In
addition, the process of integrating various businesses could cause the
interruption of, or a loss of momentum in, the activities of some or all of
these businesses as well as our ongoing business.

Our revenues and earnings could be negatively affected if we cannot anticipate
market trends, enhance our existing products and processes and develop and
commercialize new products and processes.

We believe that our future success will depend, in part, upon our ability
to anticipate rapidly changing technologies and market trends, to enhance our
existing products and processes and to develop and commercialize new products
and processes. The semiconductor industry markets we serve undergo frequent
technological changes which in turn create demand for new and improved products
and process technologies. We may not be able to improve our existing products
and process technologies or to develop and market new products and technologies
that will be cost-effective or introduced in a timely manner or accepted in the
marketplace. Our failure to develop or introduce enhanced and new products and
processes in a timely manner may negatively affect our revenues and earnings.

We are subject to operational, financial, political and exchange rate risks due
to our significant level of international operations and sales.

For the years ended December 31, 1997, 1998 and 1999, revenues outside the
United States accounted for 30.0%, 31.9% and 39.0%, respectively, of our
revenues for those years. We anticipate that international sales will continue
to account for a significant portion of our revenues. As a result, our
operations are subject to risks inherent in international business activities,
including:

. export controls;

. unexpected changes in legal and regulatory requirements;

7
<PAGE>

. policy changes affecting the markets for semiconductor technology;

. changes in tariffs, exchange rates and other barriers;

. political and economic instability;

. difficulties in accounts receivable collection;

. difficulties in managing resellers or representatives;

. difficulties in staffing and managing international operations;

. difficulties in protecting our intellectual property outside the United
States; and

. potentially adverse tax consequences.

Although our sales to date have been predominantly denominated in U.S.
dollars, the value of the U.S. dollar in relation to other currencies may also
adversely affect our sales to customers outside the United States. In addition,
the recent acquisitions of Newform and MST have increased the amount of our
operations conducted in Europe with European currency. Also, expenses and
revenues of a portion of certain of our businesses are denominated in South
Korean, Taiwanese, German or Belgian currency and are exposed to risks
customarily associated with currency fluctuations. Any significant volatility
in South Korean, Taiwanese, German or Belgian currency, as it relates to
invested capital in our respective businesses in those countries, could have a
material adverse impact on stockholders' equity as reflected in currency
translation adjustments in our financial statements. We do not hedge our
exposure with respect to such fluctuations. To the extent that we expand our
international operations or change our pricing practices to denominate prices
in other currencies, we will be exposed to increased risks of currency
fluctuations.

Certain of our businesses conduct a material portion of their activities in
Asia, primarily South Korea and Taiwan. Volatile economic conditions in the
region or in those countries, or instability in the currency of those countries
or in those countries' capital markets, may negatively impact our revenues and
earnings.

Our revenues would suffer if our major customers reduce their purchases of our
products or services.

In 1999, sales to our top five customers totaled approximately 13.5% of our
revenues. Our relationships with these customers are subject to various risks,
including:

. termination, reduction or modification in the event of changes in the
customer's requirements or budgetary constraints;

. risks of potential disclosure of our confidential information to third
parties; and

. the failure or inability of a customer to perform its prime contract
with its customer.

Our revenues would suffer if our major customers reduce their purchases of our
products or services or secure alternative sources for products or services.
Based on the current trend toward consolidation in the semiconductor industry,
we expect that our customer base will continue to become more concentrated with
a limited number of customers accounting for a more significant portion of our
revenues.

We may have difficulty responding to rapidly changing semiconductor technology,
materials and processes and face competition from existing technologies.

Semiconductor technology, materials and processes change rapidly. We may
not be successful if we cannot keep pace with such advances. We are evaluating
a number of new opportunities to

8
<PAGE>

commercialize our core technology, but these opportunities may not lead to
commercial products that are timely or competitive. The technological advances
of others may render our current products or development efforts obsolete, and
other equipment or materials may prove more advantageous to customers in the
markets we serve. In addition, certain of our current technologies face
competition from other existing technologies which may be superior to or more
cost-effective than our current technologies and products.

We face intense competition from a variety of sources, including larger
companies.

The markets for semiconductor thin film materials, packaging and delivery
systems, sensors, environmental equipment and thin film deposition services are
intensely competitive. A number of domestic and international companies engage
in commercial activities in the markets we serve. Many of these companies have
substantially greater financial, research and development, manufacturing and
marketing resources than we do. In addition, as this industry evolves, other
competitors may emerge. To remain competitive, we must continue to invest in
and focus upon research and development and product and process innovation. We
may not be successful if we cannot compete on:

. price;

. technical capabilities;

. quality;

. customer service; and

. the ability to provide full market-basket solutions to customers that
are increasingly seeking to streamline their vendor relationships.

We may incur various tax liabilities in connection with our acquisition of
Advanced Delivery and Chemical Systems that exceed our security for these
liabilities and which may negatively affect our earnings, cash flow and cash
position.

The former securityholders of Advanced Delivery and Chemical Systems have
agreed to indemnify us for possible tax liabilities of ADCS. As security for
these potential liabilities, the former securityholders of ADCS delivered into
escrow a portion of the shares of common stock they received in connection with
our acquisition of ADCS. We and the former securityholders of ADCS have
divergent views on any potential exposures related to the various tax matters
for which there will be indemnification. The former securityholders of ADCS
believe that any exposure would be immaterial. We believe that any successful
challenge to the tax matters is not probable. While the possible exposures are
difficult to quantify, we believe that, regardless of the probability that
liabilities arise, the potential exposures could range from $0 to $22 million
depending on the tax matter. We have been notified by the Internal Revenue
Service of an assessment of $2.1 million for certain of these tax matters.
Although we believe that this assessment is without merit and we intend to
vigorously defend our position on these tax matters, we cannot predict whether
we will be successful in defending against the assessment or the amount of any
final assessment against us. We have agreed that minimum amounts must be
reached before we have a right to recover our losses. The current value of the
shares held in escrow provides indemnity towards the upper range of the
potential exposures. A possibility exists that the losses could exceed the
value of the shares held in escrow because the shares held in escrow are too
few in number or too low in value to adequately compensate us for these losses.
In any event, if we incur actual tax liabilities, they will negatively affect
our earnings, cash flow and cash position.

Any prolonged disruption in manufacturing our products could negatively impact
our business.

The manufacture of semiconductors and related materials and equipment
involves highly complex manufacturing processes. We have established
manufacturing facilities for many of our

9
<PAGE>

products, including semiconductor environmental equipment, thin film materials,
packaging and delivery systems, substrates and coated wafers. We have also
established a facility to fabricate, test and assemble semiconductor thin
films, devices and circuits. In addition, we subcontract for the manufacture of
a significant portion of our gas delivery systems. Any prolonged disruption in
manufacturing our products, whether due to technical or labor difficulties,
delay or inability to obtain sufficient quantities of production input or
equipment, destruction or damage to any facility, termination of our
relationship with subcontractors or other reasons, could negatively impact our
ability to deliver products to customers. To be financially successful, we must
manufacture our products in commercial quantities, at acceptable costs and on a
timely basis, which we may not be able to do.

Our business could be adversely affected if we cannot protect our proprietary
technology or if we infringe on the proprietary technology of others.

Our proprietary technology aids our ability to compete effectively with
other companies. Although we have been awarded, have filed applications for, or
have been licensed under, numerous patents in the United States and other
countries, these patents may not fully protect our technology or competitive
position. Further, our competitors may apply for and obtain patents that will
restrict our ability to make and sell our products.

Our competitors may intentionally infringe our patents. Third parties may
also assert infringement claims against us in the future. The defense and
prosecution of patent suits are both costly and time-consuming, even if the
outcome is favorable to us. Outside the United States, such proceedings can be
extremely expensive, and their outcome very unpredictable. An adverse outcome
in the defense of a patent suit could subject us to significant liabilities to
third parties or require us to license rights from third parties or to cease
selling our products. We also rely on unpatented proprietary technology that
others may independently develop or otherwise obtain access to. Our inability
to maintain the proprietary nature of our technologies could negatively affect
our revenues and earnings.

We face the risk of product liability claims.

The manufacture and sale of our products, which include thin film and other
toxic materials, involve the risk of product liability claims. In addition, a
failure of one of our products at a customer site could interrupt the business
operations of the customer. Our existing insurance coverage limits will not be
adequate to protect us from all liabilities that we might incur in connection
with the manufacture and sale of our products if a successful product liability
claim or series of product liability claims brought against us exceeds our
insurance coverage.

Our business is subject to substantial liabilities for failure to comply with
environmental regulations.

We use, generate and discharge toxic or otherwise hazardous chemicals and
wastes in our manufacturing, processing and research and development
activities. As a result, we are subject to a variety of governmental
regulations related to the storage, use and disposal of these materials. Our
failure to comply with present or future laws could result in fines or other
liabilities being imposed on us, suspension of production or a cessation of
operations.

The various premises we occupy, particularly the premises in Danbury,
Connecticut, may have been contaminated prior to occupancy. We are not aware of
any environmental investigation or action by government agencies involving
these premises. However, under federal and state statutes and regulations, a
government agency may seek to recover its response costs and/or require future
remedial measures from both operators and owners of property where releases of
hazardous

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<PAGE>

substances have occurred or are ongoing. The prior occupant of the Danbury,
Connecticut premises has agreed to indemnify us for remediation costs in
connection with any pre-existing, on-site contamination or environmental
condition. However, this indemnification may not prove adequate to cover any
liability imposed on us related to the environmental condition of the premises
or the cost of defending an environmental action, either of which could be
substantial.

Our activities may also result in our being subject to additional
regulation. Such regulations could require us to acquire significant additional
equipment or to incur other substantial expenses to comply with environmental
laws. Our failure to control the use of hazardous substances could subject us
to substantial financial liabilities.

Provisions of our charter documents and Delaware law could discourage potential
acquisition proposals and could delay, deter or prevent a change in control.

Provisions of our certificate of incorporation and bylaws could make it
more difficult for a third party to acquire, or could discourage a third party
from attempting to acquire, a majority of our outstanding voting stock. These
provisions provide for:

. a classified board of directors;

. a prohibition on stockholder action through written consents;

. a requirement that special meetings of stockholders be called only by
the chairman of the board or the board of directors;

. advance notice requirements for stockholder proposals and nominations;

. limitations on the ability of stockholders to make changes in the board
of directors; and

. the authority of the board to issue, without stockholder approval,
preferred stock with such terms as the board may determine.

We will also be afforded the protections of Section 203 of the Delaware
General Corporation Law, which could have similar effects.

SPECIAL NOTE REGARDING FORWARD-LOOKING INFORMATION

This prospectus contains or incorporates "forward-looking statements"
within the meaning of Section 27A of the Securities Act of 1933 and Section 21E
of the Securities Exchange Act of 1934. You can identify these statements by
forward-looking words such as "believes", "anticipates", "plans", "expects",
"may", "will", "intends", "estimates" and similar words. We can give no
assurance that we will actually achieve these plans, intentions or
expectations. Our actual results could differ materially from the plans,
intentions and expectations disclosed in these forward-looking statements. We
have included important factors in the cautionary statements above that we
believe could cause our actual results to differ materially from our forward-
looking statements. We do not intend to update information contained in any of
our forward-looking statements.

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<PAGE>

USE OF PROCEEDS

We estimate that the net proceeds from our sale of 1,500,000 shares of
common stock will be approximately $79.6 million, based on an assumed offering
price to the public of $56.31 per share and after deducting the estimated
underwriters' discounts and commissions and estimated offering expenses payable
by us. We will not receive any proceeds from the sale of shares of common stock
by the selling stockholders.

We expect to use the net proceeds from this offering for general corporate
purposes and working capital, including potential acquisitions to expand our
product and service offerings, capital expenditures and the funding of
research, development and commercialization programs. We cannot assure you that
we will make any acquisitions, and we have no current agreements or commitments
with respect to any acquisition that would use any of the net proceeds from
this offering. Pending these uses, we intend to invest the net proceeds of this
offering in investment-grade, interest-bearing securities.

DIVIDEND POLICY

We have never declared or paid any cash dividends on our capital stock. We
intend to retain any future earnings to finance future growth and do not
anticipate paying any cash dividends in the future. Certain financing
agreements of our subsidiaries contain limitations on the payment of dividends
without the lender's consent or in connection with a subsidiary's failure to
comply with various financial covenants.

PRICE RANGE OF COMMON STOCK

Our common stock is quoted on the Nasdaq National Market under the symbol
"ATMI". The following table sets forth, for the periods indicated, the high and
low intraday sales prices for our common stock as reported on the Nasdaq
National Market.

<TABLE>
<CAPTION>
High Low
------ ------
<S> <C> <C>
1998
First Quarter................................................. $31.19 $20.00
Second Quarter................................................ 33.75 13.25
Third Quarter................................................. 20.00 10.88
Fourth Quarter................................................ 25.38 11.25
1999
First Quarter................................................. 31.00 16.88
Second Quarter................................................ 30.00 18.25
Third Quarter................................................. 38.00 27.50
Fourth Quarter................................................ 38.00 20.81
2000
First Quarter (through March 10, 2000)........................ 59.25 29.13
</TABLE>

On March 10, 2000, the closing sale price of our common stock as reported
on the Nasdaq National Market was $56.31 per share. As of March 10, 2000, we
had approximately 267 holders of record of our common stock.

12
<PAGE>

CAPITALIZATION

The following table sets forth our capitalization as of December 31, 1999:

. on an actual basis; and

. on an as adjusted basis to reflect the net proceeds from our sale of
1,500,000 shares of common stock, at an assumed offering price to the
public of $56.31 per share and after deducting the underwriters'
discounts and commissions and estimated offering expenses payable by us.

The common stock to be outstanding after this offering is based on shares
outstanding as of December 31, 1999 and excludes 2,874,555 shares of common
stock issuable upon the exercise of options and warrants outstanding as of such
date at a weighted average exercise price of $18.94 per share.

<TABLE>
<CAPTION>
December 31, 1999
--------------------
Actual As Adjusted
-------- -----------
(unaudited)
(in thousands)
<S> <C> <C>
Cash, cash equivalents and marketable securities.......... $ 92,174 $171,819
======== ========
Total long-term debt, less current portion................ 6,280 6,280
Minority interest......................................... 1,109 1,109
Stockholders' equity:
Preferred Stock, par value $0.01: 2,000,000 shares
authorized; no shares issued and outstanding........... -- --
Common Stock, par value $0.01: 50,000,000 shares
authorized; 27,774,183 shares issued and outstanding;
29,274,183 shares issued and outstanding, as adjusted.. 278 293
Additional paid-in capital.............................. 122,536 202,166
Retained earnings....................................... 45,465 45,465
Cumulative other comprehensive income................... 6,526 6,526
-------- --------
Total stockholders' equity............................ 174,805 254,450
-------- --------
Total capitalization................................ $182,194 $261,839
======== ========
</TABLE>

13
<PAGE>

SELECTED CONSOLIDATED FINANCIAL DATA

You should read the following selected consolidated financial data along
with "Management's Discussion and Analysis of Financial Condition and Results
of Operations" and our consolidated financial statements and notes to those
statements and other financial information included or incorporated in this
prospectus. The consolidated statement of income data for the years ended
December 31, 1996, 1997, 1998 and 1999 and the consolidated balance sheet data
at December 31, 1997, 1998 and 1999 have been derived from our audited
consolidated financial statements. The consolidated statement of income data
for the year ended December 31, 1995 and the consolidated balance sheet data at
December 31, 1995 and 1996 have been derived from our unaudited consolidated
financial statements. The unaudited consolidated financial statements include
all adjustments, consisting of normal recurring accruals, which we consider
necessary for a fair presentation of our financial position and results of
operations for these periods. The historical results presented below are not
necessarily indicative of future results.

<TABLE>
<CAPTION>
Year Ended December 31,
------------------------------------------------------
1995 1996 1997 1998 1999
-------- -------- -------- -------- --------
(in thousands, except per share data)
<S> <C> <C> <C> <C> <C>
Consolidated Statement
of Income Data:
Revenues................ $115,984 $154,390 $192,012 $165,106 $196,236
Cost of revenues........ 56,780 73,673 92,561 83,419 92,970
-------- -------- -------- -------- --------
Gross profit............ 59,204 80,717 99,451 81,687 103,266
Operating expenses:
Research and
development........... 7,892 12,314 14,336 16,630 18,359
Selling, general and
administrative........ 37,162 48,435 60,593 56,925 60,305(5)
Merger costs and
related expenses...... -- 2,000(1) 9,000(3) 1,700(4) 9,914(6)
-------- -------- -------- -------- --------
Total operating
expenses.............. 45,054 62,749 83,929 75,255 88,578
-------- -------- -------- -------- --------
Operating income........ 14,150 17,968 15,522 6,432 14,688
Interest income
(expense), net......... (338) (375) (877) 2,487 3,117
Other income (expense),
net.................... (474) 94 340 539 724
-------- -------- -------- -------- --------
Income before income
taxes and minority
interest............... 13,338 17,687 14,985 9,458 18,529
Income taxes............ 4,947 4,745 8,588 4,412 7,720
-------- -------- -------- -------- --------
Income before minority
interest............... 8,391 12,942 6,397 5,046 10,809
Minority interest....... 10 151 (2) (111) (263)
-------- -------- -------- -------- --------
Net income.............. $ 8,401 $ 13,093(2) $ 6,395 $ 4,935 $ 10,546
======== ======== ======== ======== ========
Net income per share--
assuming dilution...... $ 0.36 $ 0.54(2) $ 0.25 $ 0.18 $ 0.37
======== ======== ======== ======== ========
Weighted average shares
outstanding--assuming
dilution............... 23,051 24,318 25,660 27,423 28,319
======== ======== ======== ======== ========
<CAPTION>
December 31,
------------------------------------------------------
1995 1996 1997 1998 1999
-------- -------- -------- -------- --------
(in thousands)
<S> <C> <C> <C> <C> <C>
Consolidated Balance
Sheet Data:
Cash, cash equivalents
and marketable
securities............. $ 38,256 $ 35,966 $ 32,903 $ 86,169 $ 92,174
Working capital......... 35,093 37,118 48,878 103,938 121,199
Total assets............ 105,545 125,873 153,529 208,652 232,656
Long-term debt, less
current portion........ 12,461 18,499 19,763 12,559 6,280
Minority interest....... 535 545 595 846 1,109
Total stockholders'
equity................. 54,661 66,049 83,303 152,720 174,805
</TABLE>
- --------
(1) Represents costs accrued in connection with patent litigation involving
Lawrence Semiconductor Laboratories (prior to our acquisition of that
company), which resulted in a settlement payment in May 1997.
(2) Net income and net income per share--assuming dilution in 1996 include the
effect of the treatment of our ADCS subsidiary as an S-Corporation for a
portion of 1996 (which was prior to our acquisition of ADCS). If ADCS had
been taxed as a C-Corporation for all of 1996, our net income and net
income per share--assuming dilution would have been approximately $11.6
million and $0.48, respectively, for the year ended December 31, 1996.

14
<PAGE>

(3) Represents costs incurred in investigating, analyzing and completing our
acquisitions of ADCS and Lawrence Semiconductor Laboratories.

(4) Represents costs incurred in connection with the completion of our
acquisition of NOW Technologies.
(5) Includes $2.3 million for severance for several former executives within
ATMI Materials and ATMI Technologies.
(6) Represents $3.3 million incurred in connection with the completion of our
acquisitions of MST Analytics and Newform and $7.2 million incurred in
connection with our acquisitions of Delatech, ACSI and TeloSense offset by
a reversal of $0.6 million for previously accrued merger related costs.

15
<PAGE>

MANAGEMENT'S DISCUSSION AND ANALYSIS OF
FINANCIAL CONDITION AND RESULTS OF OPERATIONS

The following discussion and analysis of our financial condition and
results of operations should be read in conjunction with "Selected Consolidated
Financial Data" and our consolidated financial statements and related notes
appearing elsewhere in this prospectus. This discussion and analysis contains
forward-looking statements that involve risks, uncertainties and assumptions.
The actual results may differ materially from those anticipated in these
forward-looking statements as a result of certain factors, including but not
limited to those set forth under "Risk Factors" and elsewhere in this
prospectus.

Overview

We have organized our operations along two business segments: ATMI
Materials and ATMI Technologies. ATMI Materials provides products that are used
in the semiconductor manufacturing process and related packaging and delivery
systems. ATMI Technologies provides products that sense and environmentally
control these materials while also providing specialized thin film deposition
services to semiconductor device manufacturers. ATMI Technologies also conducts
our venture and government funded research and development activities.

We have entered into eight mergers since 1997, each of which has been
accounted for as a pooling of interests. As a result, our consolidated
financial statements have been restated to reflect the results of these merged
companies.

Results of Operations

The following table sets forth selected financial data as a percentage of
total revenues for the periods indicated:

<TABLE>
<CAPTION>
Year Ended December 31,
-------------------------
1997 1998 1999
------- ------- -------
<S> <C> <C> <C>
Revenues........................................ 100.0% 100.0% 100.0%
Cost of revenues................................ 48.2 50.5 47.4
------- ------- -------
Gross profit.................................... 51.8 49.5 52.6
Operating expenses:
Research and development...................... 7.5 10.1 9.4
Selling, general and administrative........... 31.6 34.5 30.7
Merger costs and related expenses............. 4.7 1.0 5.1
------- ------- -------
Total operating expenses.................... 43.8 45.6 45.2
------- ------- -------
Operating income................................ 8.0 3.9 7.4
Interest income (expense), net.................. (0.5) 1.5 1.6
Other income, net............................... 0.2 0.3 0.4
------- ------- -------
Income before income taxes and minority
interest....................................... 7.7 5.7 9.4
Income taxes.................................... 4.5 2.7 3.9
------- ------- -------
Income before minority interest................. 3.2 3.0 5.5
Minority interest............................... 0.0 (0.1) (0.1)
------- ------- -------
Net income...................................... 3.2% 2.9% 5.4%
======= ======= =======
</TABLE>

16
<PAGE>

Segment Data

During 1998, we adopted FASB Statement No. 131 "Disclosure About Segments
of an Enterprise and Related Information". We have two segments: ATMI Materials
and ATMI Technologies. The reportable segments are each managed separately
because they manufacture and distribute distinct products with different
production processes. We evaluate performance and allocate resources based on
operating profit or loss, not including interest and other income or expense
and income taxes. The accounting policies of the reportable segments are the
same as those described in the summary of significant accounting policies in
our consolidated financial statements. Intercompany sales are not material
among segments or operating divisions.

The following tables provide reported results for each of these segments:

<TABLE>
<CAPTION>
Year Ended December 31,
----------------------------
1997 1998 1999
-------- -------- --------
(in thousands)
<S> <C> <C> <C>
Revenues
ATMI Materials................................. $ 83,060 $ 71,279 $ 96,711
ATMI Technologies.............................. 108,952 93,827 99,525
-------- -------- --------
Consolidated revenues.......................... $192,012 $165,106 $196,236
======== ======== ========
Operating Income
ATMI Materials................................. $ 17,757 $ 11,373 $ 19,335
ATMI Technologies.............................. 6,765 (3,241) 5,267
Merger costs and related expenses.............. (9,000) (1,700) (9,914)
-------- -------- --------
Consolidated operating income.................. $ 15,522 $ 6,432 $ 14,688
======== ======== ========
</TABLE>

Comparison of Years Ended December 31, 1999, 1998 and 1997

Revenues. Our revenues increased 18.9% to $196.2 million in 1999 from
$165.1 million in 1998, following a decrease of 14.0% in 1998 from $192.0
million in 1997. The 1999 increase in revenues was primarily attributable to
the semiconductor industry's recovery, particularly for consumable products, as
seen by ATMI Materials' 35.7% growth in revenue. ATMI Materials experienced
significant gains related to our SDS, NOW dispensing and packaging products and
liquid materials product lines in 1999 as compared to 1998. ATMI Technologies'
revenues for 1999 increased 6.1% from 1998 levels. Semiconductor manufacturing
capacity expansion began to rebound in the middle of 1999 leading to improved
sales of EcoSys environmental and sensing products and Epitronics thin film
deposition services.

Soft market conditions in 1998, evidenced by a decline in semiconductor
unit demand in the second and third quarters of 1998 and a significant
reduction in semiconductor equipment spending during most of 1998, were the
primary causes for the 14.0% revenue decline for both ATMI Materials and ATMI
Technologies when comparing 1998 with 1997. The decline in semiconductor unit
demand during 1998 slowed sales of many of ATMI Materials' product offerings.
Semiconductor manufacturing capacity expansion substantially declined during
1998, which caused a decrease in EcoSys and Epitronics product sales.

Gross Profit. Gross profit increased 26.4% to $103.3 million in 1999 from
$81.7 million in 1998. Gross margin increased to 52.6% in 1999 from 49.5% in
1998. This increase was due principally to margin growth related to
manufacturing efficiencies from increased sales and a shift in product mix
towards SDS, NOW dispensing and packaging systems and liquid materials product
lines. Gross profit decreased 17.9% to $81.7 million in 1998 from $99.5 million
in 1997. Gross margin

17
<PAGE>

decreased to 49.5% in 1998 from 51.8% in 1997, primarily as a result of less
efficient fixed cost absorption in connection with the decrease in revenues
experienced in 1998, particularly within the EcoSys, Epitronics and NOW product
lines. Volume declines within the photoresist stripping product lines, driven
by the softening semiconductor industry conditions, also contributed to the
reduction in gross margins in 1998.

Research and Development Expenses. Research and development expenses
increased 10.4% to $18.4 million in 1999 from $16.6 million in 1998. Increased
efforts to expand SDS technology beyond ion implant applications into CVD, etch
and bulk gas delivery, and continued product development activities within ATMI
Materials and the Emosyn venture resulted in growth of the research and
development efforts. As a percentage of revenues, research and development
expenses decreased to 9.4% in 1999 from 10.1% in 1998. Research and development
expenses increased 16.0% to $16.6 million in 1998 from $14.3 million in 1997.
Similar to the increase in 1999, the 1998 increase was due to the development
efforts to extend the SDS technology beyond existing applications, as well as
the development of new chemical mechanical polishing materials and increased
research efforts to expand our sensing and monitoring product lines.

Selling, General and Administrative Expenses. Selling, general and
administrative expenses increased 5.9% to $60.3 million in 1999 from $56.9
million in 1998. Despite decreases in expenses associated with decreased
administrative costs and cost savings resulting from the integration of recent
business acquisitions, expenses incurred related to the organization of our
Taiwanese subsidiary and the commencement of our enterprise system software
implementation caused selling, general and administrative expenses to increase
in 1999. Additionally, the 1999 expenses included $2.3 million in severance for
several former executives within ATMI Materials and ATMI Technologies. As a
percentage of revenues, these expenses decreased to 30.7% in 1999 from 34.5% in
1998. Selling, general and administrative expenses decreased 6.1% to $56.9
million in 1998 from $60.6 million in 1997. The 1998 decrease was primarily due
to a significant reduction in executive compensation paid to members of
management of certain acquired businesses (Delatech, ACSI and TeloSense) due to
weaker operating performance, a reduction of administrative costs resulting
from reductions in personnel and decreased commissions on lower product
revenues.

Merger Costs and Related Expenses. The 1999 operating results included
merger and related costs of $9.9 million, including $3.3 million of
professional fees and transactions costs related to our November 1999
acquisitions of MST and Newform and $2.8 million of investment banking, legal
and accounting fees in connection with the investigation, analysis and May 1999
closing of the TeloSense, Delatech and ACSI transactions. The 1999 merger
related costs included a $0.6 million reversal of previously accrued merger
costs for prior acquisitions. The acquisition of Delatech also resulted in a
$4.4 million asset impairment charge during the second quarter of 1999 for
inventory ($1.0 million) and goodwill ($3.4 million) associated with an
existing environmental equipment product line which was determined to be
impaired. The 1998 operating results included merger related charges of $1.7
million incurred in completing the NOW acquisition.

Operating Income. Operating income, including the recognition of merger
related costs, increased 128.4% in 1999 to $14.7 million from $6.4 million in
1998 which was a 58.6% decrease from $15.5 million in 1997. ATMI Materials'
operating income for 1999 increased 70.0% to $19.3 million from $11.4 million
in 1998. This increase reflected the gains made due to the improved market
conditions within the industry and increased market share penetration during
1999. The significant revenue increase in 1999 combined with stronger margins
and cost containment initiatives resulted in higher operating income within
ATMI Materials. ATMI Materials' operating income, as a percentage of revenues,
was 20.0% and 16.0% for 1999 and 1998, respectively. ATMI Technologies'
operating income improved to $5.3 million in 1999 compared to a $3.2 million
loss in 1998. The profitability increase was attributable to the growth in both
EcoSys and Epitronics revenues, the attendant

18
<PAGE>

product margin improvements and a favorable product mix shift along with an
improvement in profitability of various contract programs. Investments in
research and product development within Emosyn and our other ventures are
reflected in ATMI Technologies' operating income. ATMI Technologies' operating
income, as a percentage of revenues, was 5.3% and (3.5)% in 1999 and 1998,
respectively.

ATMI Materials' operating income declined 36.0% to $11.4 million in fiscal
1998 from $17.8 million in 1997. The revenue decline in 1998 reduced gross
margins within ATMI Materials and, combined with an increase in research and
development spending, drove the operating income decline. ATMI Materials'
operating income, as a percentage of revenues, was 21.4% in 1997. ATMI
Technologies' operating income declined to a loss of $3.2 million in fiscal
1998 compared to operating income of $6.8 million in 1997. These losses were
attributable to the severe decline in sales of EcoSys products, reduced
Epitronics operating results caused by revenue declines on a relatively fixed
cost base and an increase in research and development efforts focused on our
Emosyn business and other new business ventures.

Other Income, Net. Other income, net increased to approximately $3.8
million in 1999 from $3.0 million in 1998. The increase in 1999 related to a
significant increase in interest income due to increased cash levels on hand
throughout all of 1999 compared to only part of 1998. These increased cash
levels resulted from a public offering that was completed at the beginning of
the second quarter of 1998. Increased interest rate levels in 1999 also
resulted in increased interest income. Other income, net increased to $3.0
million in 1998 from a net expense of $0.5 million in 1997 as a direct result
of the increased cash and marketable securities that resulted from our public
offering in the first quarter of 1998. Interest expense decreased 26.5% to $1.3
million in 1999 from $1.7 million in 1998, and decreased 34.0% in 1998 from
$2.6 million in 1997. The 1999 decrease related to the retirement of a
significant debt balance related to the Delatech acquisition as well as final
payments on several equipment leases within Epitronics. The 1998 decrease was
due to a conversion of outstanding debt at ACSI into equity in late 1997 and
lower overall debt balances outstanding during 1998, as capital lease lines
were paid down and certain high-interest rate debt was retired.

Income Taxes. Income tax expense increased 75.0% to $7.7 million in 1999
from $4.4 million in 1998. Income tax expense decreased 48.6% to $4.4 million
in 1998 from $8.6 million in 1997. Our income tax expense related primarily to
United States federal, state and foreign tax liabilities, which were partially
offset by various foreign sales corporation benefits and research and
development credits. The 1999 effective tax rate was in line with statutory
rates at 42.3%. While no tax benefit was taken for a significant amount of
merger related costs in 1999, benefit was recognized based on changes in
estimates regarding the realizability of net operating loss and tax credit
carryforwards of certain acquired companies. The 1998 effective tax rate of
47.2% was higher than statutory rates because no tax benefit was taken for the
$1.7 million of merger costs related to the NOW acquisition, and no tax benefit
was recognized for operating losses sustained by ACSI in 1998. The significant
1997 effective tax rate of 57.3% was due in part to the 1997 operating results
including the $9.0 million for merger costs related to the ADCS and Lawrence
Semiconductor acquisitions for which no tax benefit was taken.

Minority Interest. Minority interest represents the 30.0% interest held by
K.C. Tech Co., Ltd. in the operations of ADCS-Korea, a South Korean chusik
hoesa, which is a joint venture established to manufacture, sell and distribute
chemicals to the semiconductor and related industries in South Korea.

Net Income Excluding Transaction Related Costs and Other Expenses. Over the
last three years, we have used mergers and acquisitions to accelerate our
growth and broaden our

19
<PAGE>

product lines. As a result of this strategy, we have incurred expenses to
consummate these transactions and merge these acquired businesses into existing
operations. Excluding these merger costs and certain severance charges related
to reorganizing the business pursuant to these acquisitions, net income from
recurring operations would have been $19.3 million, or $0.68 per share--
assuming dilution in 1999. This represents a 175.7% increase over $7.0 million,
or $0.26 per share--assuming dilution in 1998. On a comparable basis, 1997 net
income from recurring operations was $15.4 million, or $0.60 per share--
assuming dilution.

20
<PAGE>

Selected Quarterly Results of Operations

The following table sets forth certain unaudited consolidated quarterly
financial information for the eight quarters ended December 31, 1999, as well
as such data expressed as a percentage of our revenues for the periods
indicated. In the opinion of our management, this information has been prepared
on the same basis as the audited consolidated financial statements appearing
elsewhere in this prospectus and includes all adjustments (consisting only of
normal recurring adjustments) necessary to present fairly the unaudited
quarterly results when read in conjunction with our consolidated financial
statements and related notes included elsewhere in this prospectus. The results
of operations for any quarter are not necessarily indicative of future results
of operations.

<TABLE>
<CAPTION>
Quarter Ended
------------------------------------------------------------------------
Mar. 31 June 30 Sept. 30 Dec. 31 Mar. 31 June 30 Sept. 30 Dec. 31
1998 1998 1998 1998 1999 1999 1999 1999
------- ------- -------- ------- ------- ------- -------- -------
(in thousands)
<S> <C> <C> <C> <C> <C> <C> <C> <C>
Revenues................ $52,047 $44,446 $35,161 $33,452 $37,240 $49,323 $52,055 $57,618
Cost of revenues........ 23,519 23,152 20,254 16,494 18,243 23,005 24,833 26,887
------- ------- ------- ------- ------- ------- ------- -------
Gross profit............ 28,528 21,294 14,907 16,958 18,997 26,318 27,222 30,731
Operating expenses:
Research and
development........... 3,944 4,501 4,132 4,053 4,023 4,462 5,009 4,865
Selling, general and
administrative........ 15,623 14,727 12,893 13,682 12,941 15,251 13,668 18,445(1)
Merger costs and
related expenses...... -- -- 1,700 -- -- 6,800 -- 3,114
------- ------- ------- ------- ------- ------- ------- -------
Total operating
expenses.............. 19,567 19,228 18,725 17,735 16,964 26,513 18,677 26,424
------- ------- ------- ------- ------- ------- ------- -------
Operating income
(loss)................. 8,961 2,066 (3,818) (777) 2,033 (195) 8,545 4,307
Other income, net....... 112 775 907 1,232 802 924 626 1,489
------- ------- ------- ------- ------- ------- ------- -------
Income (loss) before
income taxes and
minority interest...... 9,073 2,841 (2,911) 455 2,835 729 9,171 5,796
Income taxes............ 3,271 1,332 (566) 375 1,358 1,466 2,929 1,970
------- ------- ------- ------- ------- ------- ------- -------
Income (loss) before
minority interest...... 5,802 1,509 (2,345) 80 1,477 (737) 6,242 3,826
Minority interest....... (55) (13) (3) (40) 1 (82) (110) (72)
------- ------- ------- ------- ------- ------- ------- -------
Net income (loss)....... $ 5,747 $ 1,496 $(2,348) $ 40 $ 1,478 $ (819) $ 6,132 $ 3,754
======= ======= ======= ======= ======= ======= ======= =======
<CAPTION>
Percentage of Revenues
------------------------------------------------------------------------
<S> <C> <C> <C> <C> <C> <C> <C> <C>
Revenues................ 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0% 100.0%
Cost of revenues........ 45.2 52.1 57.6 49.3 49.0 46.6 47.7 46.7
------- ------- ------- ------- ------- ------- ------- -------
Gross profit............ 54.8 47.9 42.4 50.7 51.0 53.4 52.3 53.3
Operating expenses:
Research and
development........... 7.6 10.1 11.8 12.1 10.8 9.1 9.6 8.4
Selling, general and
administrative........ 30.0 33.1 36.7 40.9 34.8 30.9 26.3 32.0(1)
Merger costs and
related expenses...... -- -- 4.8 -- -- 13.8 -- 5.4
------- ------- ------- ------- ------- ------- ------- -------
Total operating
expenses.............. 37.6 43.2 53.3 53.0 45.6 53.8 35.9 45.8
------- ------- ------- ------- ------- ------- ------- -------
Operating income
(loss)................. 17.2 4.7 (10.9) (2.3) 5.4 (0.4) 16.4 7.5
Other income, net....... 0.2 1.7 2.6 3.6 2.2 1.9 1.2 2.6
------- ------- ------- ------- ------- ------- ------- -------
Income (loss) before
income taxes and
minority interest...... 17.4 6.4 (8.3) 1.3 7.6 1.5 17.6 10.1
Income taxes............ 6.3 3.0 (1.6) 1.1 3.6 3.0 5.6 3.5
------- ------- ------- ------- ------- ------- ------- -------
Income (loss) before
minority interest...... 11.1 3.4 (6.7) 0.2 4.0 (1.5) 12.0 6.6
Minority interest....... (0.1) (0.0) (0.0) (0.1) 0.0 (0.2) (0.2) (0.1)
------- ------- ------- ------- ------- ------- ------- -------
Net income (loss)....... 11.0% 3.4% (6.7)% 0.1% 4.0% (1.7)% 11.8% 6.5%
======= ======= ======= ======= ======= ======= ======= =======
</TABLE>
- --------
(1) Includes $2.3 million for severance for several former executives within
ATMI Materials and ATMI Technologies.

Our quarterly results have varied significantly and are likely to continue
to vary significantly due to a number of factors including the general demand
for semiconductors, the cyclical nature of the semiconductor manufacturing
equipment market, our product mix, our success in developing, introducing

21
<PAGE>

and shipping new products, competition, the timing of significant orders from,
and shipments to, customers, the timing and market acceptance of new products,
seasonality of sales and the effect of various non-recurring expenses.

Liquidity and Capital Resources

To date, we have financed our activities through cash from operations, the
sale of equity, external research and development funding and various lease and
debt instruments. Our working capital increased to $121.2 million at December
31, 1999 from $103.9 million at December 31, 1998 and $48.9 million at December
31, 1997.

Net cash provided by operations was approximately $13.1 million during
1999, resulting primarily from improvements in working capital, as compared to
cash provided from operations of $13.3 million during 1998. The cash flow from
operations for 1999 related primarily to net income adjusted for non-cash
charges partially offset by the increase in working capital items, primarily
accounts receivable. In addition, the $9.9 million of merger costs and related
expenses, expensed in 1999, reduced the cash generated from operations by
approximately $4.3 million, as $4.4 million were non-cash charges and
approximately $1.2 million remained unpaid at December 31, 1999. The
improvement in working capital for 1999 was primarily caused by a decrease in
other assets and increases in accounts payable, accrued expenses and other
liabilities. The $1.7 million of merger costs and related expenses, expensed in
the third quarter of 1998, reduced the cash generated from operations by
approximately $1.1 million, as approximately $0.6 million remained unpaid at
December 31, 1998. Net cash provided by operations in 1997 was approximately
$4.1 million. Additionally, the $9.0 million of merger costs and related
expenses, expensed in the fourth quarter of 1997, reduced the cash generated
from operations by approximately $7.0 million, as approximately $2.0 million
remained unpaid at December 31, 1997.

Our investing activities included capital expenditures of $10.2 million,
$15.0 million, and $9.1 million in the years 1999, 1998 and 1997, respectively.
The 1999 expenditures were made primarily to support the growth experienced at
several of our manufacturing facilities. The 1998 expenditures primarily
related to installation of additional manufacturing capacity in Danbury,
Connecticut, San Jose, California and our two Texas facilities. The 1997
expenditures included both the installation of SDS manufacturing capacity in
the Danbury, Connecticut facility and an increase in epitaxial capacity in
Epitronics' Arizona facilities.

Among other investing activities, in 1998 we invested approximately $47.9
million raised primarily from a public offering of our common stock into
marketable securities for future working capital requirements and potential
merger and acquisition activities. In July 1997, prior to our acquisition of
MST, it used $5.6 million to purchase four businesses. In addition, we sold
$0.8 million in marketable securities in 1997.

Our financing activities included a March 1998 registered underwritten
public offering of 5,428,000 shares of our common stock. Of such shares, we
sold 2,257,000 shares and certain of our stockholders sold 3,171,000 shares. We
received net proceeds from the offering of approximately $62.4 million.

At December 31, 1999, we financed a significant portion of our capital
equipment purchases, particularly the silicon epitaxial capacity, through
capital leases with about $3.8 million of capital lease obligations
outstanding. During 1999 and 1998, we made payments on capital leases of
approximately $2.5 million and $2.8 million, respectively. Financial
institutions also provided collateral-based loans for other equipment
purchases. In 1999, we made $9.1 million of note payments and during 1998, we
made payments on notes of approximately $6.7 million, with the most significant
payment being the retirement of a mortgage on the Mesa, Arizona Epitronics
facility. Our

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NOW business has an industrial revenue bond arrangement outstanding in the
amount of $2.3 million, which was used for equipment and improvements at its
manufacturing facility and corporate office. At December 31, 1999, $13.2
million of loans, bonds and financing remained outstanding. Our management
believes that our debt service obligations can be adequately satisfied by cash
flows from operations.

We believe that our existing cash balances, marketable securities, existing
sources of liquidity and anticipated funds from operations will satisfy our
projected working capital and other cash requirements through at least the end
of 2000. However, we also believe the level of financing resources available to
us is an important competitive factor in our industry and we may seek
additional capital prior to the end of that period. Additionally, we consider,
on a continuing basis, potential acquisitions of technologies and businesses
complementary to our current business. There are no present agreements with
respect to any such acquisitions. However, any such transactions may affect our
future capital needs.

Year 2000 Compliance

We formed an internal compliance team to evaluate our internal information
technology infrastructure and application systems and other non-IT
infrastructure systems to determine whether such systems would operate
correctly with regard to the import, export and processing of date information,
including correct handling of leap years, in connection with the change in the
calendar year from 1999 to 2000, and to evaluate the Year 2000 issue with
respect to the systems of third party partners and suppliers with which we have
a material relationship.

We completed an inventory analysis and risk assessment. As previously
planned and budgeted, we upgraded our core IT Systems to incorporate additional
desired features and functionality including Year 2000 compliant operators. We
completed the necessary upgrades to make the recently acquired businesses Year
2000 compliant by December 31, 1999. In connection with such upgrades, we
expect that our core IT Systems are Year 2000 compliant, and no significant
issues have arisen to date from the calendar change to January 2000. We do not
expect that any additional costs of addressing the Year 2000 issue will have a
material adverse impact on our financial position and results of operations or
cash flows.

We also completed a non-IT system inventory analysis and risk assessment.
As a result of the analysis, no remediation actions were required in order to
be Year 2000 compliant. We believe the number of non-IT systems is relatively
small and, therefore, do not expect that any additional costs of addressing the
Year 2000 issue for these systems will have a material adverse impact on our
operations or our financial position, results of operations or cash flows.

We completed a third party inventory and risk assessment and verified
material Year 2000 compliance of these systems by December 31, 1999. We believe
the number of material third party systems is relatively small. However, until
Year 2000 compliance of all third party systems if ascertained, the risk to our
operations and any additional costs relating to these systems is unknown. We
believe that any problems that might arise would involve third party systems
rather than our internal systems. We believe that majority of the risks
associated with Year 2000 non-compliance have been averted as the calendar
turned. Any further risk might be the partial shutdown of a supplier or
strategic partner and its inability to provide supplies and services to us on a
timely basis. We developed a contingency plan addressing potential issues,
ensuring that adequate levels of critical supplies used in our manufacturing
processes were on hand at the end of 1999.

We tested our products for Year 2000 compliance and determined that all of
our products currently available for sale have either successfully passed Year
2000 compliance testing or are not subject to Year 2000 compliance because such
products do not import, export or process date information in any manner.

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We incurred approximately $600,000 relating to inventory analysis and risk
assessment of potential Year 2000 difficulties. The funds to cover the costs
incurred were derived from general operations. The costs primarily related to
desktop compliance and standardization to Year 2000 compliance. These Year 2000
expenditures were within our planned organizational budgets and included the
costs of reviewing key operating systems. No IT Systems projects were deferred
because of problems associated with the Year 2000 Issue.

Operations Outside the United States

For the years ended December 31, 1999, 1998 and 1997, export sales outside
the United States, including Asia and Europe, accounted for 39.0%, 31.9%, and
30.0%, respectively, of our revenues. We anticipate that our sales outside the
United States will continue to account for a significant percentage of our
revenues. The November 1999 acquisitions of MST and Newform have increased our
European operations. In addition, we have a wholly-owned subsidiary in Taiwan
where we sell and service several of our product lines. We also have a wholly-
owned subsidiary in South Korea that manufactures and markets environmental
abatement equipment in South Korea and a joint venture agreement with K.C. Tech
pursuant to which we have a 70.0% interest in ADCS-Korea, a South Korean chusik
hoesa, which manufactures, sells and distributes thin film materials to the
semiconductor and related industries in South Korea.

Quantitative and Qualitative Disclosures About Market Risks

Interest Rate Risk

As of December 31, 1999, our cash included money market securities and
commercial paper. Due to the short duration of our investment portfolio, an
immediate 10% change in interest rates would not have a material effect on the
fair market value of our portfolio, therefore, we would not expect our
operating results or cash flows to be affected to any significant degree by the
effect of a sudden change in market interest rates on our securities portfolio.

Foreign Currency Exchange Risk

A substantial portion of our sales are denominated in U.S. dollars and, as
a result, we have relatively little exposure to foreign currency exchange risk
with respect to sales made. This exposure may change over time as business
practices evolve and could have a material adverse impact on our financial
results in the future. We do not use forward exchange contracts to hedge
exposures denominated in foreign currencies or any other derivative financial
instruments for trading or speculative purposes. The effect of an immediate 10%
change in exchange rates would not have a material impact on our future
operating results or cash flows.

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BUSINESS

Market data used throughout this prospectus were obtained from internal
surveys and from industry publications, including information generated by
Dataquest Inc. and the Semiconductor Industry Association. We have not
independently verified such information. This information was not commissioned
by, or prepared at the request of, us or any of our affiliates. Similarly,
internal surveys, while believed to be reliable, have not been verified by an
independent source.

We have further refined our market focus to target only specialty materials
used in front-end semiconductor manufacture. These specialty materials are used
in eight key process steps that are used repetitively to add functionality to a
silicon wafer. In recent years, the semiconductor industry has grown worldwide
and front-end manufacturing processes have become increasingly complex,
resulting in rapidly changing requirements for semiconductor materials. We have
capitalized on the growth of the semiconductor industry in general, and front-
end processing in particular, through:

. a comprehensive research and development program that has provided a
stream of proprietary and patented products for this market;

. a strategy of delivering a complete materials solution to our customers
including materials, packaging, delivery systems, sensing and abatement;
and

. an aggressive mergers and acquisitions effort that has allowed us to
more rapidly move towards one-stop purchasing for our customers.

We have organized our operations along two business segments: ATMI
Materials and ATMI Technologies. ATMI Materials provides:

. a broad range of ultrahigh-purity semiconductor materials; and

. semiconductor materials packaging and delivery systems.

ATMI Technologies provides:

. sensors for the workplace and environment that detect materials as they
move through the workplace;

. point-of-use environmental equipment that abates materials; and

. specialty thin film deposition services that provide coated wafers
directly to our customers.

We also conduct our venture activities and our government funded research and
development activities through ATMI Technologies.

Our business has evolved to consist of an equal mix of consumables and
services that track wafer starts, or the number of silicon wafers processed
into fully functional semiconductor devices, and equipment purchases, which
generally track the expansion of industry capacity. Consequently, we believe
that our overall business is less volatile than that of a typical semiconductor
capital equipment supplier. ATMI Materials and ATMI Technologies accounted for
approximately 49% and

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51%, respectively, of our revenues in 1999, and approximately 43% and 57%,
respectively, of our revenues in both 1998 and 1997.

Semiconductor Industry Background

The semiconductor industry has grown in recent years as the use of
semiconductor devices has proliferated in a wide variety of consumer and
industrial products, especially in computing, networking and communications
equipment. According to the Semiconductor Industry Association, the
semiconductor industry achieved worldwide sales in 1999 of $149 billion and is
estimated to achieve worldwide sales of over $200 billion in 2001. This
increase in demand for semiconductor devices has been fueled by the ability of
semiconductor manufacturers to deliver products with:

. consistently enhanced performance characteristics and functionality;

. improved reliability;

. increased memory capacity; and

. reduced size, weight, power consumption and cost.

These advances have been made possible by innovations in the fabrication
processes, equipment and the materials used in manufacturing advanced
semiconductor devices. At the same time, as the construction and management of
fabrication facilities has become more complex, semiconductor manufacturers
have sought to streamline their supplier relationships and reduce the number of
suppliers upon which they rely. In turn, this has driven significant
consolidation among the providers of semiconductor capital equipment and
materials and materials delivery systems.

Semiconductor devices are manufactured by repeating a complex series of
process steps on a wafer substrate, usually made of silicon. The primary
process steps include various kinds of materials deposition (physical vapor
deposition, chemical vapor deposition, electrochemical deposition, ion implant
and spin-on), etch, wafer preparation (chemical mechanical polishing) and
patterning (photolithography).

During deposition processes, several layers of conducting, semiconducting
or insulating thin films are formed on a wafer. Precise and reliable control of
the deposition of these films is vital to the ultimate performance of an
individual device.

The most mature processes for thin film deposition and modification are
physical vapor deposition, also known as PVD or sputtering, ion implantation
and spin-on deposition. In PVD, which is used primarily for the deposition of
conducting or metal layers, a high energy beam is directed at a high purity
metal target which in turn causes the displacement of metal atoms that are
showered over the wafer coating it with a thin metallic film. Ion implantation
is a gas based process used principally to modify (or dope) semiconducting
layers with a high energy beam of material that is "implanted" into an existing
thin film. In spin-on deposition, a spinning wafer is treated with a solution
of materials and solvent. The solvent is vaporized leaving the material in
place which is usually further heat treated to form the desired thin film.

Chemical vapor deposition, or CVD, is a newer process used in the
deposition of semiconducting and insulating thin films. In the CVD process,
wafers are placed in a sophisticated reaction chamber, and a specially designed
gas or vaporized liquid material is introduced.

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Simultaneously, a form of energy, such as heat or plasma, is added to the
reactor to cause the decomposition of the material being introduced. As a
result of this decomposition, a thin film of material is deposited on the
surface of the wafer. The advantages of CVD over PVD based processes include:

. the relative thinness of the films applied to the wafer;

. conformality (ability to coat evenly, especially in holes and trenches
designed into the device);

. purity; and

. the ability to coat large areas.

These advantages have led to rapid growth in sales of reactors and related CVD
process consumables and equipment. Consumables and related equipment include
the raw materials used in the CVD process and the delivery systems required to
transport the materials around a semiconductor plant and to a reactor.

An even more recently developed process called electrochemical deposition,
or ECD, is now growing rapidly as a result of the industry's desire to use
copper as the conducting layer in certain devices. In ECD, the wafer is
submerged in a bath of copper electroplating solution which, when appropriately
charged, deposits a thin film of copper on the wafer.

Etch is a process that selectively erodes away certain thin film materials.
It is carried out either "dry" with corrosive gases or "wet" with energized
liquids. Chemical mechanical polishing, or CMP, is used to prepare a wafer for
photolithography. As wafers are processed, thin film thicknesses inevitably
vary across the surface of the wafer. Due to the fine line widths used in
photolithography, present day wafers need to be perfectly flat. CMP flattens
the processed wafer by polishing the wafer using a mechanical polishing pad and
a slurry, which is an abrasive solution containing solid materials and
chemicals which selectively erodes away the appropriate excess materials.

Photolithography is the process whereby patterns are developed on the wafer
surface. The process is begun by spinning a photosensitive material called a
"photoresist" or "resist" onto the wafer surface and shining light through a
patterned photomask to selectively harden the resist. The resist is then
developed by stripping or otherwise removing excess resist material and
allowing for the fabrication of the wafer's circuitry.

Materials and Delivery Systems

The market for semiconductor thin film materials has expanded with the
growth of the market for semiconductor devices. The design of new thin film
deposition materials and equipment to transport these materials around a
semiconductor plant has experienced ongoing innovation. This innovation has
been driven by the demand for expanding semiconductor device capabilities and
corresponding decreases in circuit dimensions. Safe and effective thin film
deposition requires dedicated systems designed to deliver and vaporize
precursor materials for deposition in reactors without contamination or
inadvertent release of toxic gases.

Because thin film materials are consumables, the market for these materials
and delivery systems generally tracks wafer starts, as opposed to the market
for equipment, which generally tracks investment in new plants. The thin film
materials market is also segmented into a wide variety of material types and
forms. For example, many thin film precursors are now sold as pressurized
gases, which allows for easy transport around a typical semiconductor
manufacturing plant. However, many of these gases are toxic and/or hazardous,
leading to the development of safer alternatives including the use of liquid or
solid materials and the adoption of gas handling technologies and delivery
systems that minimize the danger of a catastrophic release of toxic gas. We
estimate that

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the total annual market in 1999 for specialty thin film deposition, etch, CMP,
photolithography materials and delivery systems exceeded $3 billion.

Materials Packaging. Semiconductor materials have exceptional purity
requirements due to the extremely low tolerances for impurities and
particulates in semiconductor processing. Gases are in a form whereby
particulates can be readily managed. Liquids and solids, however, require
special packaging to minimize exposure to air and particulates.

Materials Sensing and Monitoring. Semiconductor gases pose unique toxicity
and environmental difficulties. As a result, the need for devices to sense and
warn personnel of leaks or possible catastrophic releases of these gases is
compelling. To that end, a market for toxic gas sensing devices and systems has
grown up in tandem with the semiconductor industry. Semiconductor fabs are now
outfitted with a high level of sensing technology to protect the workplace and
the environment. Furthermore, this technology is being integrated with factory
operations to prevent and/or minimize damage or productivity of the plant and
its personnel. We believe the market for this type of materials sensing
equipment exceeded $150 million in 1999.

Sensors are also required to monitor materials purity and concentration.
The ability to integrate sensors to control processing equipment is also
critical to the productivity of the high capital intensive semiconductor fabs.
So-called "in-process sensing" is growing rapidly with the increasing
complexity of semiconductor processing.

Environmental Equipment

The use of gas and vapor based processes has led to the development of
environmental equipment designed to abate gaseous effluent. For example, less
than 40% of the materials entering a CVD reactor are deposited as a thin film.
The remainder of the source materials, and certain by-products, constitute an
effluent stream containing toxic and hazardous material that must be abated to
meet increasingly strict worldwide environmental, safety and health
regulations. Traditionally, abatement has been accomplished by the use of
"whole plant" environmental systems, which aggregate the effluents from an
entire facility. However, variations in the processes used and the drive for
increased productivity have led to the growth of point-of-use environmental
systems in which a single environmental unit is attached to a single reactor.
This approach provides for superior abatement because the system can be tuned
to the unique hazards of a particular effluent stream. In addition, point-of-
use environmental systems can improve plant productivity by reducing downtime
associated with servicing environmental systems. We believe the market for this
type of point-of-use environmental equipment exceeded $200 million in 1999.

Deposition Services

The demand for higher performance integrated circuits and discrete
semiconductor devices has driven the use of epitaxial wafers in a wide variety
of applications. Epitaxial, or "epi", wafers are wafers on which CVD thin films
have been deposited. A merchant market for epitaxial wafers, primarily silicon
epitaxial wafers, has in recent years developed due to the high degree of
expertise and significant capital expenditures required by epitaxy. According
to Dataquest Inc., this market was $2.0 billion in 1998. This market is
subdivided into "generic" wafers for high volume applications such as dynamic
random access memory, or DRAM, and "specialty" wafers for use in applications
such as automotive electronics and sensors, silicon-based low power
telecommunications circuits, analog power controls and robust application-
specific integrated circuits. We believe that specialty epi products accounted
for approximately 15% of the total epi wafer market or $300 million in 1998 and
will constitute a significant portion of the overall growth of the merchant
market for epitaxial wafers.

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The continued drive for improved device performance and new applications
for integrated circuits has led to the development and commercialization of
alternative semiconductor technologies. A newer generation of devices has
emerged that uses epitaxial wafers made of III-V and wide bandgap materials, as
opposed to silicon, to achieve this improved performance. III-V semiconductors,
including gallium arsenide and indium phosphide, are finding increasing use in
wireless communication devices where high frequency performance is critical, in
optoelectronic devices where the electronic structure of the III-V
semiconductors allows energy-efficient light generation and in solar cells for
satellite applications where efficient generation of electricity is critical.
Wide bandgap semiconductors, such as silicon carbide and gallium nitride, offer
advantages in high power, optoelectronic and high temperature devices. We
believe the market for all wide bandgap materials for both electronic and
optoelectronic applications was approximately $9.0 billion in 1999.

ATMI's Strategy

Our objective is to establish and enhance leadership positions in each of
the market segments we serve. Our strategy consists of the following key
elements:

. We target high growth, high margin specialty markets that use our core
materials technologies and require products that are consumed in the
production process.

. We seek to provide full market-basket solutions, or "one-stop shopping",
through innovation and acquisitions in each of our target markets to
help our customers streamline supplier relationships.

. We provide added value through advanced packaging and dispensing systems
designed to meet the demands of users for greater levels of purity,
productivity, safety and environmental responsiveness.

. We leverage our technology leadership by investing extensively in
developing proprietary and patented materials and materials handling
technology which we use to commercialize new products to meet customer
requirements.

. We form strategic alliances, including joint development programs and
collaborative marketing efforts, to accelerate the introduction of our
products into markets that have manufacturing and/or distribution
barriers.

Businesses and Products

We conduct our operations through two primary business segments: ATMI
Materials and ATMI Technologies.

ATMI Materials

We believe ATMI Materials is one of the fastest growing suppliers of
ultrahigh purity semiconductor materials and related packaging and delivery
systems to the semiconductor industry. We have taken advantage of the changes
in the market for materials and delivery systems by:

. developing and commercializing a wide range of "front-end" semiconductor
materials;

. commercializing innovative bulk delivery systems which automatically
deliver materials of the highest purity and consistency to a process;

. developing innovative packaging systems that allow for the introduction
of low volatility liquids and solids to semiconductor processes;

. developing and commercializing patented low-pressure gas delivery
systems for safe handling and delivery of toxic and hazardous gases to
semiconductor process equipment; and

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. developing manufacturing processes to meet the critical purity and
integrity requirements of the microelectronics industry.

In meeting the needs of our customers, which include semiconductor device
manufacturers, chemical suppliers and OEMs located throughout the world, and
anticipating their future requirements, we seek:

. to offer the most complete line of consumable and delivery and packaging
system products;

. to offer the most consistent, highest purity materials available;

. to offer the most reliable, innovative equipment products;

. to improve the level of customer service, technical support and response
offered and to remain cost-effective to our customers;

. to meet customer needs for statistical quality and process control and
dock-to-stock programs; and

. to continue to meet the industry's needs for advanced materials required
for future generation devices.

Products and Services. ATMI Materials has four primary product lines, which
consist of liquid materials, liquid delivery systems, gas delivery systems and
advanced packaging and dispensing systems. ATMI Materials also provides
services relating to each of these product lines.

Liquid Materials. We produce a broad range of materials that are used in
making semiconductor devices. In addition to the widely used CVD precursors
such as TEOS and related dopants, we also sell thin film materials used in
other semiconductor manufacturing processes, including phosphorous and boron
halides used for doping by diffusion processing. We also manufacture and sell
source reagents that allow CVD of advanced materials, including titanium
nitride, platinum, copper, tantalum oxide, lead zirconate titanate, strontium
bismuth tantalate and barium strontium titanate thin films.

All of these thin films must be of very high purity in order to function
properly within the device, particularly with respect to unwanted metallic
contamination. We believe that our cleaning and container technology produces
the most consistent, highest purity chemicals in the industry and ensures their
quality as delivered into the reactor.

We also produce a wide range of liquid products for photoresist stripping,
edge bead removal, developing and cleaning. In addition, we recently entered
the rapidly growing market for CMP slurries. We now provide high performance
oxide polishing slurries, and we expect to introduce advanced metal slurries.

Liquid Delivery Systems. We design, manufacture and sell proprietary
continuous refill and delivery systems. These systems are designed to deliver
ultrahigh-purity thin film materials to the CVD reactors under the desired
physical conditions. Our delivery systems include stainless steel ampules,
stainless steel MINIBULK canisters, stainless steel SKINNIBULK canisters,
quartz bubblers, bulk chemical delivery cabinets, level sensing systems, manual
and continuous refill systems and other application-specific equipment.

We believe that our continuous refill systems enhance the performance of
the process tools they support by eliminating process downtime resulting from
canister changes. Typically, process tools must cease operation when canister
changes are made to replenish source material. Our bulk refill systems allow
continuous delivery of source material. In addition to the elimination of the
downtime associated with canister changes, this configuration also minimizes
the atmospheric and moisture contamination that can occur during these change-
outs.

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Gas Delivery Systems (the SDS or Safe Delivery System). Our patented SDS
product line uses a standard gas cylinder containing an adsorbent material. The
cylinder is filled with gas under conditions such that the gas is adsorbed onto
the material, and the SDS cylinder is at sub-atmospheric pressure, minimizing
any potential leak of hazardous gas and allowing more gas to be introduced into
the cylinder than would be possible under traditional high pressure conditions.
Consequently, material delivery via SDS is safer and provides significantly
higher rates of productivity than traditional methods. Since most semiconductor
processes operate at reduced pressure and the gas can be desorbed or released
from the SDS under vacuum, it can be installed and operated like a conventional
high-pressure gas cylinder. These advantages have led major chip manufacturers
to adopt this technology.

To date, we have introduced products using the SDS technology to deliver
several gases, including arsine, phosphine, boron trifluoride, silicon
tetrafluoride and germanium tetrafluoride. Each is used to "dope" silicon
wafers using ion implant processes. All of these SDS products are available in
different size cylinders, and some have different adsorbents that allow for
additional gas capacity within a cylinder. These products are manufactured by
us, and for us by Matheson Gas Products, our exclusive distributor for SDS used
in ion implant applications.

We also believe that significant markets for SDS exist outside ion implant.
We are now commercializing SDS for CVD applications. We have also undertaken
extensive development efforts to identify new markets and products for the SDS
technology. We believe that certain etch gases used in the semiconductor
industry and certain gases normally delivered in bulk within the semiconductor
industry are possible candidates for the SDS process.

Advanced Packaging and Delivery Systems. We manufacture three different
types of NOWPak container assemblies: "Bag-in-a-Bottle"; "Bag-in-a-Can"; and
"Bag-in-a-Drum". Each features a pre-cleaned collapsible inner liner, or "bag",
inside a rugged, high-density polyethylene or stainless steel overpack. The
standard liner film is made of polytetrafluoroethylene which allows virtually
all chemicals to be delivered to the manufacturing process in an unaltered
state. The empty inner liner is easily removed for waste consolidation, and the
outer shell is recyclable or returnable for insertion of a new replacement
liner.

The largest market for NOWPak's packaging is materials for photoresists.
These materials are typically packaged in one liter through ten liter Bag-in-a-
Bottle containers. The NOWPak's market applications for photoresists used in
the manufacture of active matrix flat panel displays as well as for the
pharmaceutical, biotech and laboratory markets are typically in 18-20 liter
Bag-in-a-Bottle and Bag-in-a-Can containers. Additionally, applications have
recently expanded beyond photolithography chemicals in the semiconductor niche
to include ancillary chemicals, CMP slurries and process chemicals for which
the new 200 liter Bag-in-a-Drum is well suited.

We also produce packages for high purity solids under the Newform brand
name. We make high-purity flexible Ultra Clean packaging for the semiconductor
and pharmaceutical industries. With our Newform products, we package critical
solids-sputter targets, wafer and disc shippers, cleanroom parts and container
overwraps. With the NOWPak liquid packaging system and Newform solids
packaging, we are addressing all facets of critical packaging for the
microelectronics market.

ATMI Technologies

We have taken advantage of our expertise in semiconductor materials
technology to build a comprehensive product portfolio around this core
technology. Effectively, ATMI Materials' business ends with the delivery of a
specialty material to a semiconductor industry process tool. Through its common
core technical understanding of these materials, ATMI Technologies delivers
products and

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services that allow its customers to manage materials flow through the
remainder of the semiconductor factory. ATMI Technologies addresses its
customers' needs by providing:

. sensing products that protect both the workplace and the environment;

. monitoring products for certain processes that ensure the quality of the
thin film product being produced;

. a full range of abatement products that remove potential environmental
threats from the process exhaust stream; and

. specialty thin film deposition services for those customers who do not
desire to perform this operation within their own facilities.

As a result of this strategy, we believe ATMI Technologies is the leading
supplier of sensing products, point-of-use abatement systems and specialty
epitaxial deposition services to the worldwide semiconductor industry. ATMI
Technologies also manages our ventures portfolio, which includes the Emosyn
smart card device product line and our optoelectronic materials activities,
until these ventures mature to market critical mass.

Products and Services. ATMI Technologies includes three primary product
lines and services, which consist of sensing products, point-of-use
semiconductor environmental equipment and deposition services.

Sensing Products. We provide life safety systems to the semiconductor
industry. Because the gases used in semiconductor manufacturing are so toxic,
manufacturers must install systems which protect employees from accidental
releases. We believe that we are now the only company offering a range of
technologies capable of detecting all of the gases used in semiconductor
manufacturing. Combined with our worldwide systems integration capabilities, we
are able to provide customers with a single contact for the design,
installation, commissioning and sustaining service on complete life safety
systems.

Satellite series electrochemical sensors provide distributed sensors
located at each point requiring gas detection. Electrochemical sensors provide
cost effective and reliable detection of most gases used in semiconductor
fabrication. This sensor's self-check feature and auto-calibration feature
provide maximum reliability and ease of use and are the leading sensor
technology for acid gases in a fab.

ACM Air Composition Monitors allow the fab to determine the exact
composition of any gas that is emitted in the fab. This system allows the fab
to determine exactly the composition of unknown odors that fab personnel may
detect. It also is the only known detection device in the industry that can
measure NF3 without the need to decompose it into another species for
detection.

TGM Toxic Gas Monitors use molecular emissions spectroscopy to measure and
speciate toxic gases. This system is the leading technology for sensing the
very toxic hydride gases used to dope semiconductor films.

H2M Hydrogen Monitors use a patented acoustical technology that measures
the time of flight of hydrogen in a enclosed tube. We believe this system is
the only system on the market that can detect hydrogen without interference
from other gases such as hydrocarbons. As a result, we believe this system is
the most reliable way to detect hydrogen.

Semi-Chem Fluid Process Monitors are unique liquid sensing devices that use
multiple liquid analysis technologies. These devices analyze the signals they
receive with complex algorithms and measure the precise assay of materials that
effect the overall yield of a device.

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We also provide a unique and high value added liquid chemical analysis and
control tool. We believe that we are a market leader in the analysis and
control of the active ingredients in CMP slurries. In addition, we believe that
we are well positioned to provide leading technology to the semiconductor
copper plating market through product development activities with industry
leaders.

Point-of-Use Semiconductor Environmental Equipment. We believe we are the
only provider of point-of-use environmental equipment offering all of the key
technologies for effluent gas abatement to the semiconductor industry: dry
chemical; liquid; and active oxidation. As a result of this broad product line,
we believe we are a global market leader in the manufacture and sale of point-
of-use semiconductor effluent abatement equipment. Our strategy is to grow our
market share through the continued development and acquisition of new
semiconductor environmental products and services. We believe that this full
line of semiconductor environmental products, coupled with a comprehensive
service and sensing strategy, will allow for continued market penetration by
this business.

We have four primary environmental equipment product lines. Each of the
four major point-of-use products has cost of ownership advantages for
semiconductor customers in certain applications such as CVD, ion implant and
etch.

Novapure dry chemical scrubbers adsorb and concentrate hazardous effluent
through the use of consumable resins at rates many times that of conventional
effluent treatment methods. We believe that, through our patented adsorption
materials, we are a market leader for point-of-use semiconductor effluent dry
scrubbing throughout the world. This technology is typically used for ion
implant applications, in conjunction with our SDS product line. It is also used
for etch and certain CVD applications.

Vector wet scrubbers are designed for cost effective removal of acidic and
high particulate bearing gases commonly used in the wafer fabrication process.
Vector scrubbers recirculate scrubbing water, minimizing overall water use, and
are effective in removing high particulate effluent and, with its optional air-
oxidation inlet, pyrophoric gases. The Vector scrubber is typically used in CVD
and etch applications. It is the leading treatment system for multi-wafer
chamber CVD tools.

Guardian active oxidation scrubbers treat a variety of combustible
materials used in semiconductor processing. The Guardian product line is
designed for high reliability and very high flow rates of combustible gases
typically used in CVD and flat panel display applications.

Delatech CDO oxidation and water treatment scrubbers use a combination of
thermal oxidation and wet scrubbing to treat solid particulate and acid gas
applications in a single unit. This system can also be used to treat PFCs
(perfluorinated compounds believed to be responsible for global warming). This
system is the industry's leading treatment solution for single wafer chamber
CVD tools.

Deposition Services. In addition to deposition on patterned wafers, CVD
thin film processes are used to prepare bare wafers prior to the fabrication of
integrated circuits to provide the wafer surfaces with the desired uniformity
of electrical and physical properties. Such CVD thin film deposition is
referred to as epitaxial deposition, and these wafers when processed are
referred to as epitaxial, or "epi", wafers. The complexity, sensitivity and
capital intensive nature of the CVD processes used for epitaxy have created a
market for epitaxial thin film deposition services, or contract manufacture of
epi wafers using CVD processes.

ATMI Technologies operates a service business providing specialty epitaxial
deposition services for silicon, III-V and wide bandgap wafers. Desired
electrical and physical properties of the epitaxial layers are specified by the
customer and developed in collaboration with us. The properties of the
epitaxial layers are selected to maximize the performance of the customer's
integrated circuit or

33
<PAGE>

device while maximizing yield and minimizing cost. Our fundamental competitive
advantages include the manufacture of high quality epitaxial layers with high
yield. In addition, we differentiate ourselves by offering quality epitaxial
deposition services with fast turnaround and in flexible volumes.

We believe that we are the only provider offering CVD thin film deposition
services for each of the key materials used in semiconductor devices today, and
that we are now a world leader in specialty epitaxial deposition services. Our
strategy is to maximize market share through the continued development and
acquisition of new semiconductor thin film products and services. A key element
of the business strategy is to work with the customer in the early stages of
product development to ensure that proven epitaxial processes are in place when
the decision is made to expand into manufacturing.

We provide commercial epitaxial deposition services for silicon and III-V
materials. III-V epitaxial wafers are finding increasing use in wireless
communications, satellites and optoelectronics for data and telecommunication
markets. Epitaxial services for wide bandgap semiconductors and several new
products in silicon and gallium arsenide are in development. We are currently
engaged in several collaborations to develop wide bandgap epitaxial wafers for
future optoelectronic, sensor and power device products. Furthermore, we are
developing a silicon germanium epitaxial process for use in silicon-based
heterojunction devices for high speed communication and computation integrated
circuits and an ultrathin silicon on sapphire process for use in high
frequency, low power applications. We are also continuing development of
epitaxial structures for gallium arsenide-based electronics devices including
heterojunction bipolar transistors and high electron mobility transistors in
collaboration with our customers.

Ventures. We also maintain an active in-house venture program. The primary
goal of this program is to develop next-generation semiconductor materials
technology that is beyond the product development scope of our existing core
businesses. The research and development funding that we apply to this program
is enhanced through federal government contract or partner funding in nearly
all cases.

Smart Card Device Venture. We are currently developing and commercializing
integrated circuits for use in smart cards. Smart cards are credit card-like
devices that operate through a chip on the card as opposed to the more familiar
magnetic strip. The smart card is read through insertion into a "reader" that
clamps down on the device and simultaneously powers it up and performs a
multitude of operations. The smart card market is growing rapidly, especially
in Europe, in the mobile phone, health care and transportation industries. Long
term, we expect that smart cards will see wide use in secure internet
transactions.

We entered this market to leverage certain proprietary advanced non-
volatile materials technology. To facilitate the development of these
integrated circuits, we have entered into a strategic alliance with a
subsidiary of SMH Swatch, the largest watch maker in Switzerland, to design,
develop, manufacture and distribute these products. In November 1998, we also
entered into a strategic alliance with Xicor, Inc. that gives us the right to
become Xicor's exclusive sales channel for Xicor integrated circuit products
targeting smart card applications. We also hold an option to purchase this
product line beginning in 2001.

Our first smart card products are targeted at the fast-growing market for
micro-controller-based smart card IC's. The combination of our expertise in
non-volatile memory technology with SMH Swatch's expertise in ultra-low power
and radio frequency technology has enabled the launch of a device called
"Theseus" which provides high density, speed, power and memory partitioning.
Our approach to memory technology design provides a smart card solution that
significantly reduces the major problem of time-to-market for the card
manufacturers with no increase in device size. We are now working to specify
our products with smart card manufacturers, and in the fourth quarter of 1999,
we shipped our first commercial product.

34
<PAGE>

Other Venture Activities--Optomaterials. We have oriented much of our
effort in the ventures program area towards the development of optoelectronic
materials, especially gallium nitride. We believe that our unique technology in
this area, in both substrate and epi layer manufacture, will allow us to enter
new rapidly growing markets as either a supplier of these materials or as a
partner in the development of advanced optoelectronic devices such as blue
laser diodes and high performance light emitting diodes.

Customers, Sales and Marketing

We sell and distribute our products worldwide, both directly and through
manufacturers' representatives. Many of our customers have relationships with
more than one of our segments or are acting as collaborators on our development
programs.

We distribute our materials and delivery system products to end-use
customers, chemical suppliers and equipment suppliers through our direct sales
force in North America, Europe and Taiwan, and through regional manufacturing
representatives in other parts of Asia. Additionally, our equipment product
lines are marketed and sold to semiconductor equipment OEMs, who in turn resell
to end users. NOWPak containers are generally sold to chemical suppliers. The
chemical companies then sell their high purity chemicals in NOWPak containers
at the request of end-users. Newform packaging products have historically been
sold directly to semiconductor and pharmaceutical companies, predominately in
Europe. We sell our SDS product into the ion implant market through an
exclusive distribution agreement with Matheson.

The businesses within ATMI Technologies distribute products both directly
and through various manufacturing representatives.

We distribute our point-of-use environmental equipment and life safety
monitoring equipment through manufacturers' representatives throughout the
world. Direct sales personnel serve as regional managers who coordinate the
representatives' activity within their respective regions. Additionally, we
market environmental equipment product lines directly to semiconductor end-user
facility managers to provide full-fab environmental and monitoring solutions as
well as installation and on-going service.

We market and sell our thin film deposition services and epitaxial wafers
primarily on a direct basis. In particular, silicon epi wafers and services are
sold directly throughout the world. Wide bandgap and III-V epitaxial wafers are
sold directly in North America and through distributors and agents in Europe
and Asia.

Substantially all of our sales are to customers in the worldwide
semiconductor industry. Our results of operations, therefore, are materially
dependent upon economic and business conditions in the semiconductor industry.
The semiconductor industry has historically experienced significant growth;
however, periods of reduced semiconductor unit demand and manufacturing
overcapacity could result in significantly reduced demand for semiconductor
materials, capital equipment and wafer processing services.

35
<PAGE>

Manufacturing

The following table summarizes the location, products manufactured at and
size of our various manufacturing facilities as of December 31, 1999.

<TABLE>
<CAPTION>
Location Products Square Footage
-------------------- --------------------------------- --------------
<S> <C> <C> <C>
ATMI Bloomington, MN . chemical containers and dis- 70,000
Materials pensing systems
Burnet, TX . liquid materials 30,000
. delivery systems
Carrollton, TX . liquid materials 30,000
. delivery systems
Danbury, CT* . liquid materials 72,000
. delivery systems
. SDS
Anseong, South Korea . liquid materials 9,000
Hoegaarden, Belgium . packaging products 30,000
ATMI Buffalo Grove, IL . monitoring equipment 33,000
Technologies
Danbury, CT* . proprietary adsorbents for gas 72,000
treatment products
. wide bandgap epitaxial wafers
. high performance thin films
Mesa, AZ . specialty silicon epitaxial wa- 33,000
fers
Napa, CA . point-of-use environmental 40,000
equipment
Phoenix, AZ . III-V epitaxial wafers 15,000
San Jose, CA . point-of-use environmental 45,000
equipment
Bonn, Germany . monitoring equipment 12,000
Munich, Germany . monitoring equipment 30,000
Seoul, South Korea . point-of-use environmental 3,000
equipment
</TABLE>
- --------

*Corporate Headquarters

36
<PAGE>

Competition

ATMI Materials

Our primary competitors in semiconductor materials in the United States are
the Schumacher Division of Air Products Corporation and the Diffusion Systems
Division of Arch Chemical (in CVD precursors) and the EKC division of ChemFirst
Corporation and the ACT division of Ashland Chemical (in photolithography
ancillaries). We compete with these companies outside of the United States and
also with Yamanaka Hutech Corporation and Kojundo in Asia, and Merck in Europe.
There are a number of other smaller participants in these markets.

There are currently no direct competitors to our patented SDS product.
Several companies, however, provide gases in high-pressure containers that
compete with the process capability of SDS. There are numerous domestic and
foreign companies that offer products that compete with our packaging and
chemical dispensing system products. However, we believe that our ability to
compete in the markets for containers and dispensing systems is dependent
largely upon our patented NOWPak technology and our proven ability to
continually enhance and improve our products and technologies.

ATMI Technologies

Our competitors in effluent abatement include CS GmbH, Ebara, Japan
Pionics, and the Edwards Division of British Oxygen Corporation. Our primary
competitors in sensing products include MDA in the United States and Europe and
Riken in Japan.

We have different competitors in each of our primary deposition services
areas. In silicon epi, we compete with Moore Technologies, Reaction
Technologies and a number of specialty wafer manufacturers with their own epi
capabilities. In some product areas, we compete with the major silicon wafer
manufacturers including Wacker, Mitsubishi Silicon America and Sumitomo. In
III-V epi, we compete with Kopin, Epitaxial Products International, Emcore and
a number of other manufacturers.

Our Emosyn business is evolving as a commercial presence in a very large
smart card IC marketplace. Several large companies are also working to provide
semiconductor devices into that marketplace, including Phillips, Atmel and
Samsung.

Research and Development

Our research and development expenses consist of personnel and other direct
and indirect costs for internally funded project development. Our external
funding is almost exclusively from various agencies of the federal government.
We also participate in joint development efforts with certain semiconductor
manufacturers and semiconductor equipment OEMs. Total sums expended for
research and development for the years ended December 31, 1999, 1998 and 1997
were $23.1 million, $22.5 million and $22.2 million, respectively. Of those
amounts, $4.7 million, $5.9 million and $7.9 million, respectively, were
externally funded and are classified within cost of revenues on our
consolidated financial statements, and $18.4 million, $16.6 million and $14.3
million, respectively, were internally funded expenditures and are classified
as research and development expenses on our consolidated financial statements.
Total research and development expenditures from internal and external funding
represented 11.8%, 13.6% and 11.6% of our revenues in 1999, 1998 and 1997,
respectively.

37
<PAGE>

Strategic Alliances

We form strategic alliances, including joint development programs and
collaborative marketing efforts, to accelerate the introduction of our products
into markets that have manufacturing and/or distribution barriers. These
programs have led to significant technological advances, including the
development of proprietary advanced materials and semiconductor manufacturing
processes. Most of our strategic alliances are with leading semiconductor
manufacturers or OEMs, such as IBM, Lucent Technologies, Micron Technology,
Siemens and Texas Instruments, each of which has participated with us in
advanced materials development programs. These programs enhance our core
technology base, promote the introduction of targeted products and reduce our
need to make research and development and capital expenditures.

Patents and Proprietary Rights

We have made a significant investment in securing intellectual property
protection for our technology and products. We protect our technology by, among
other things, filing patent applications for technology considered important to
the development of our business. We also rely upon trade secrets, unpatented
know-how, continuing technological innovation and the aggressive pursuit of
licensing opportunities to help develop and maintain our competitive position.

As of March 10, 2000, we had been awarded 172 United States patents and had
163 United States patent applications pending. Foreign counterparts of certain
of these applications have been filed, or may be filed at an appropriate time.
We decide on a case-by-case basis whether, and in what countries, we will file
counterparts of a United States patent application outside the United States.
Our United States patents expire between 2006 and 2019. We also hold 20 United
States registered trademarks. We are actively using all United States
trademarks.

Our ability to compete effectively with other companies will depend, in
part, on our ability to maintain the proprietary nature of our technology.
Although we have been awarded, have filed applications for, or have been
licensed under numerous patents in the United States and other countries, there
can be no assurance concerning the degree of protection afforded by these
patents or the likelihood that pending patents will be issued.

We require all employees and most consultants, outside scientific
collaborators, sponsored researchers and other advisors to execute
confidentiality agreements upon the commencement of employment or consulting
relationships with us. These agreements provide that all confidential
information developed or made known to the individual during the course of the
individual's relationship with us is to be kept confidential and not disclosed
to third parties except in specific circumstances. All of our employees have
entered into agreements providing for the assignment of rights to inventions
made by them while employed by us.

Employees

As of December 31, 1999, we employed a total of 902 individuals, including
355 in sales and administration, 462 in operations and 85 in research and
development. Of these employees, 38 hold Ph.D. degrees and 21 hold other
advanced degrees in electrical engineering, materials science, chemistry,
physics or related fields. None of our employees are covered by collective
bargaining agreements. We have not experienced any work stoppages, and consider
our relations with our employees to be strong.

38
<PAGE>

Legal Proceedings

We have been notified by the Internal Revenue Service of an assessment of
$2.1 million for certain tax matters related to our Advanced Delivery and
Chemical Systems subsidiary. Although we believe that this assessment is
without merit and we intend to vigorously defend our position on these tax
matters, we cannot predict whether we will be successful in defending against
the assessment or the amount of any final assessment against us.

In December 1998, a former office employee (Cheryl Reed) of ADCS initiated
a legal proceeding against ADCS and us in the District Court for the 33rd
District in Burnet, Texas, alleging personal injuries to her minor child (then
unborn) allegedly resulting from her exposure to various chemicals while
employed by ADCS. The plaintiffs have claimed damages of $25.0 million and
unspecified exemplary damages. We have denied the plaintiffs' legal allegations
and are vigorously defending this action. While we cannot predict the outcome
of this proceeding at this time, we believe it is without merit.

In addition, in the normal course of business, we are involved in various
lawsuits and claims. Although we cannot determine the ultimate outcome of any
of these legal proceedings at this time, management, including internal
counsel, does not believe that the outcome of these proceedings, individually
or in the aggregate, will have a material adverse effect on our financial
position or overall trends in results of operations.

39
<PAGE>

MANAGEMENT

The following table sets forth information about our directors and
executive officers as of March 10, 2000.

<TABLE>
<CAPTION>
Name Age Position
---- --- --------
<S> <C> <C>
Eugene G. Banucci, Ph.D.... 56 President, Chief Executive Officer and Chairman
of the Board
Peter S. Kirlin, Ph.D...... 39 Executive Vice President--ATMI Technologies
Douglas S. Neugold......... 41 Executive Vice President--ATMI Materials
Daniel P. Sharkey.......... 43 Vice President, Chief Financial Officer and
Treasurer
Mark A. Adley.............. 40 Director
Robert S. Hillas........... 51 Director
Kam Law, Ph.D.............. 46 Director
Stephen H. Mahle........... 54 Director
Stephen H. Siegele......... 40 Director
</TABLE>

Eugene G. Banucci, Ph.D., a founder of ATMI, has served as President, Chief
Executive Officer and Chairman of the Board since 1986.

Peter S. Kirlin, Ph.D. has served as Executive Vice President of ATMI
Technologies since 1995. From 1991 to 1995, Dr. Kirlin served as Vice President
of the Microelectronics division of ATMI and General Manager of the former
NovaMOS division of ATMI. From 1988 to 1991, Dr. Kirlin served as Director of
Superconductor Materials and Electronics for ATMI.

Douglas A. Neugold has served as Executive Vice President of ATMI Materials
since February 1999. In January 1998, Mr. Neugold joined ATMI as Vice President
of the former NovaSource division and served as President of that division from
July 1998 to February 1999. Previously, Mr. Neugold served in a variety of
executive and managerial positions with the Electronic Materials Division of
Johnson Matthey, a specialty chemicals company. From 1995 to 1997, he served as
Vice President, and later as President of its Semiconductor Packages business,
and from 1993 to 1995, he served as Director of Asian Operations.

Daniel P. Sharkey has served as Chief Financial Officer since joining ATMI
in 1990 and has served as Vice President and Treasurer since 1993.

Mark A. Adley has served as a director of ATMI since 1991. Since 1996, Mr.
Adley has been a Managing Director at Credit Suisse First Boston Corporation,
an investment banking firm, where he was a Director from 1994 to 1996.

Robert S. Hillas has served as a director of ATMI since 1987. Mr. Hillas
has been the President, Chief Executive Officer and Chairman of the Board of
Envirogen, Inc., an environmental systems and services company, since April
1998. From 1993 to April 1998, Mr. Hillas served as a Managing Director of E.M.
Warburg, Pincus & Co. LLC, an asset management firm. Mr. Hillas is also a
director of Transition Systems, Inc. and United States Filter Corporation.

Kam Law, Ph.D. has served as a director of ATMI since April 1999. Dr. Law
has been the Senior Vice President of Applied Komatsu Technology, a flat panel
display manufacturing equipment supplier, since October 1998. From April 1998
to October 1998, Dr. Law served as General Manager

40
<PAGE>

of the Global Product Organization of AKT, and from 1997 to April 1998, he
served as Executive Managing Director and General Manager--CVD Products at AKT.
From 1994 to 1997, Dr. Law served as Senior Director of AKT.

Stephen H. Mahle has served as a director of ATMI since 1996. Mr. Mahle has
been Senior Vice President of Medtronic, Inc., a medical device manufacturer,
and President of its cardiac rhythm management business since January 1998.
From 1995 to 1998, he was President of the Brady Pacing Business, a division of
Medtronic. From 1989 to 1995, Mr. Mahle served as Vice President and General
Manager of the Brady Pacing Business.

Stephen H. Siegele has served as a director of ATMI since October 1997. He
served as Vice Chairman of ATMI's board of directors from February 1999 to
December 1999 and served as President of ATMI's former ADCS division from
October 1997 through December 1999. Mr. Siegele served as the President and
Chief Executive Officer of ADCS from February 1994 until October 1997, when it
was acquired by ATMI. From 1988 to 1994, Mr. Siegele served as Vice President
of ADCS.

41
<PAGE>

SELLING STOCKHOLDERS

The following table sets forth information about the beneficial ownership
of our common stock by each of the selling stockholders as of March 10, 2000.
Each of the stockholders has sole voting and investment power over the shares
of common stock shown as beneficially owned.

<TABLE>
<CAPTION>
Shares Beneficially Shares Beneficially
Owned Prior to Number Owned After
Offering of Shares Offering
----------------------- Being -----------------------
Selling Stockholder Number Percent Offered Number Percent
- ------------------- ------------ ------------------- ------------ ----------
<S> <C> <C> <C> <C> <C>
Stephen H. Siegele (1).. 2,525,534 9.0% 1,295,712 1,229,822 4.2%
The Lawrence Family
Trust, 1995(2)......... 1,400,922 5.0% 300,000 1,100,922 3.7%
RL Partners LLC......... 4,764 * 4,288 476 *
</TABLE>
- --------
* Less than 1%.
(1) Stephen H. Siegele has served as a director of ATMI since October 1997. He
served as Vice Chairman of ATMI's board of directors from February 1999 to
December 1999 and served as President of ATMI's former ADCS division from
October 1997 through December 1999.
(2) Lamonte H. Lawrence is a trustee and beneficiary of the Lawrence Family
Trust, 1995. Mr. Lawrence served as a director of ATMI from October 1997 to
October 1999.

42
<PAGE>

DESCRIPTION OF CAPITAL STOCK

Our authorized capital stock consists of 50,000,000 shares of common stock,
par value $0.01 per share, and 2,000,000 shares of preferred stock, par value
$0.01 per share. The following summary of our securities and provisions of our
certificate of incorporation and our bylaws is not intended to be complete and
is qualified by reference to the provisions of applicable law and to our
certificate of incorporation and bylaws.

Common Stock

As of March 10, 2000, 28,042,250 shares of our common stock were issued and
outstanding, held by approximately 267 holders of record. In addition, 788,664
shares of common stock are reserved for future grants under our various stock
plans. Furthermore, as of March 10, 2000, there were outstanding options and
warrants to purchase 3,059,253 shares of common stock. Subject to preferences
that may be applicable to any outstanding preferred stock, holders of our
common stock are entitled to share ratably in all of the assets of ATMI
available for distribution to holders of common stock upon the liquidation,
dissolution or winding up of the affairs of ATMI. Our common stock has no
preemptive or conversion rights or other subscriptions rights. There are no
redemption or sinking fund provisions applicable to our common stock, and the
outstanding shares of common stock are fully paid and nonassessable.

Stockholders are entitled to one vote for each share of common stock held
of record on matters submitted to a vote of stockholders. Our common stock does
not have cumulative voting rights. As a result, the holders of more than 50% of
the shares of common stock voting for the election of directors can elect all
of the directors if they choose to do so, and, in such event, the holders of
the remaining shares of common stock will not be able to elect any person or
persons to the board of directors.

Preferred Stock

Our board of directors has the authority, subject to any limitations
established by law, without further stockholder approval, to issue from time to
time up to 2,000,000 shares of preferred stock in one or more series. The board
of directors may fix the number of shares, designations, powers, preferences
and special rights of the preferred stock. The preferences, powers, rights and
restrictions of different series of preferred stock may differ. The issuance of
preferred stock could decrease the amount of earnings and assets available for
distribution to holders of our common stock or adversely affect the rights and
powers, including voting rights, of holders of common stock.

The purpose of authorizing our board of directors to issue preferred stock
and determine its rights and preferences is to eliminate delays associated with
a stockholder vote on specific issuances. The issuance of preferred stock,
while providing desirable flexibility in connection with possible acquisitions
and other corporate purposes, could make it more difficult for a third party to
acquire, or could discourage a third party from attempting to acquire, a
majority of the outstanding voting stock of ATMI. We have no present plans to
issue any shares of preferred stock.

Delaware Law and Certain Charter and Bylaw Provisions

Classified Board of Directors. Our certificate of incorporation and bylaws
provide for our board of directors to be divided into three classes of
directors: Class I, Class II and Class III, as nearly equal in number as is
reasonably possible. Each director is elected for a three-year term, with one
class of directors being elected at each annual meeting of stockholders. In the
event of any increase or decrease in the authorized number of directors,
directorships will be apportioned among the classes by our board of directors
to ensure that no one class has more than one director more

43
<PAGE>

than any other class, to the extent possible. Since only one third of the
directors of the classified board of directors are subject to election each
year, it is more difficult for the stockholders to change the management of
ATMI than if the board of directors were not classified. In addition, the
presence of a classified board of directors could make it more difficult for a
third party to acquire, or could discourage a third party from attempting to
acquire, control of ATMI and, therefore, may limit the price that certain
investors might be willing to pay in the future for shares of our common stock.

Changes in Board of Directors. Our certificate of incorporation and bylaws
provide that vacancies on the board of directors may be filled by a vote of a
majority of the board of directors then in office. Also, our bylaws provide
that any increase or decrease in the number of directors requires the approval
of a majority of the directors then in office. These provisions of our
certificate of incorporation and bylaws could make it more difficult for a
third party to acquire, or could discourage a third party from attempting to
acquire, control of ATMI and, therefore, may limit the price that certain
investors might be willing to pay in the future for shares of our common stock.

Stockholder Action. Our certificate of incorporation and bylaws provide
that any action required or permitted to be taken by the stockholders may be
taken only at a duly called annual or special meeting of the stockholders and
may not be taken by written consent. These provisions could have the effect of
delaying until the next annual stockholders' meeting stockholder actions which
are favored by the holders of a majority of our outstanding voting securities,
because special meetings of stockholders may be called only by a majority of
the board of directors or the Chairman of the Board. These provisions may also
discourage another person from making a tender offer for our common stock,
because such person, even if it acquired a majority of our outstanding voting
securities, would be able to take action as a stockholder only at a duly called
stockholders' meeting and not by written consent.

Advance Notice Provisions for Stockholder Nominations of Directors and
Stockholder Proposals. Our certificate of incorporation and bylaws establish
advance notice procedures with regard to the nomination, other than by or at
the direction of the board of directors, of candidates for election as
directors and with regard to other business to be brought by stockholders
before an annual meeting of stockholders.

Our nomination procedure requires that a stockholder give to our Secretary
prior written notice, in proper form, of a planned nomination for the board of
directors. Our bylaws specify the requirements for the form and timing of that
notice. If the Chairman of the Board determines that a person was not nominated
in accordance with our nomination procedure, such person will not be eligible
for election as a director.

Under our business procedure, a stockholder seeking to have any business
conducted at an annual meeting must give prior written notice, in proper form,
to our Secretary. Our bylaws specify the requirements for the form and timing
of that notice. If the Chairman of the Board determines that the other business
was not properly brought before such meeting in accordance with our business
procedure, such business will not be conducted at the meeting.

Although our bylaws do not give the board of directors any power to approve
or disapprove stockholder nominations for the election of directors or of any
other business desired by stockholders to be conducted at an annual or any
other meeting, our bylaws:

. may have the effect of precluding a nomination for the election of
directors or precluding the conduct of business at a particular annual
meeting if the proper procedures are not followed; or

. may discourage or deter a third party from conducting a solicitation of
proxies to elect its own slate of directors or otherwise attempting to
obtain control of ATMI, even if the conduct of such solicitation or such
attempt might be beneficial to ATMI and its stockholders.

44
<PAGE>

Delaware Takeover Statute. We are subject to Section 203 of the Delaware
General Corporation Law. Subject to certain exceptions, this section prohibits
certain publicly held Delaware corporations from engaging in a "business
combination" with an "interested stockholder" for a period of three years
following the date of the transaction in which the person became an interested
stockholder, unless the business combination is approved in a prescribed manner
or certain other exemptions apply. For purposes of Section 203, "business
combination" is defined broadly to include reorganizations, asset sales and
other transactions resulting in a financial benefit to the interested
stockholder. Generally, an "interested stockholder" is any person or entity
who, together with affiliates and associates, owns (or within the three
immediately preceding years did own) 15% or more of the corporation's voting
stock.

Limitation on Liability and Indemnification of Directors. Our certificate
of incorporation contains certain provisions permitted under Delaware corporate
law relating to the liability of directors. To the extent permitted by Delaware
corporate law, the provisions eliminate a director's personal liability for
monetary damages for a breach of fiduciary duty. The provisions also indemnify
directors and officers to the fullest extent permitted by Delaware corporate
law.

Registration Rights

The holders of a maximum of 9,246,143 shares of our common stock and
warrants to purchase approximately 10,000 shares of our common stock have
certain rights with respect to the registration of these shares under the
Securities Act of 1933. If we propose to register any of our securities under
the Securities Act, either for our own account or the account of other security
holders exercising registration rights, those holders are entitled to notice of
the registration and are entitled to include in the registration their shares
of common stock at our expense, subject to certain conditions and limitations,
including the right of the underwriters of any offering to limit the number of
shares included in the registration. In addition, holders of approximately
3,921,456 of these shares have the right to require us to file a registration
statement under the Securities Act at our expense with respect to these shares
of common stock, and we are required to use our best efforts to effect the
registration, subject to certain conditions and limitations. Of the
approximately 9,256,143 shares of common stock subject to registration rights,
1,600,000 shares will be sold in this offering, approximately 1,100,922 shares
are freely tradable without registration under the Securities Act but may not
be sold for a period of 45 days following the date of this prospectus without
the consent of the underwriters pursuant to a lock-up agreement between the
underwriters and the holder of these shares, approximately 5,330,399 shares are
covered by or have been sold under effective resale registration statements and
the remaining 1,224,822 shares are subject to a lock-up agreement between the
underwriters and the holder of these shares and may not be sold for a period of
90 days following the date of this prospectus without the consent of the
underwriters. We believe, therefore, that the holders of shares with
registration rights are unlikely to exercise their rights.

We are required to bear substantially all registration and selling expenses
in connection with the registration of registrable shares in these
registrations. In addition, we will, subject to certain limitations, indemnify
any selling stockholders against certain liabilities, including liabilities
under the Securities Act, in connection with these registrations.

Transfer Agent and Registrar

The transfer agent and registrar for our common stock is Boston EquiServe
L.P.

45
<PAGE>

UNDERWRITING

ATMI, the selling stockholders and the underwriters for the offering named
below have entered into an underwriting agreement with respect to the shares
being offered. Subject to certain conditions, each underwriter has severally
agreed to purchase the number of shares indicated in the following table.
Goldman, Sachs & Co., Banc of America Securities LLC, Deutsche Bank Securities
Inc. and Prudential Securities Incorporated are the representatives of the
underwriters.

<TABLE>
<CAPTION>
Number of
Underwriters Shares
------------ ---------
<S> <C>
Goldman, Sachs & Co.............................................
Banc of America Securities LLC..................................
Deutsche Bank Securities Inc....................................
Prudential Securities Incorporated..............................
---
Total.......................................................
===
</TABLE>

If the underwriters sell more shares than the total number set forth in the
table above, the underwriters have an option to buy up to an additional 225,000
shares from ATMI and 240,000 shares from certain of the selling stockholders to
cover such sales. They may exercise that option for 30 days. If any shares are
purchased pursuant to this option, the underwriters will severally purchase
shares in approximately the same proportion as set forth in the table above.

The following tables show the per share and total underwriting discounts
and commissions to be paid to the underwriters by ATMI and the selling
stockholders. These amounts are shown assuming both no exercise and full
exercise of the underwriters' option to purchase additional shares.

<TABLE>
<CAPTION>
Paid by ATMI
-------------------------
No Exercise Full Exercise
----------- -------------
<S> <C> <C>
Per Share....................................... $ $
Total........................................... $ $
<CAPTION>
Paid by the Selling
Stockholders
-------------------------
No Exercise Full Exercise
----------- -------------
<S> <C> <C>
Per Share....................................... $ $
Total........................................... $ $
</TABLE>

Shares sold by the underwriters to the public will initially be offered at
the initial price to public set forth on the cover of this prospectus. Any
shares sold by the underwriters to securities dealers may be sold at a discount
of up to $ per share from the initial price to public. Any such securities
dealers may resell any shares purchased from the underwriters to certain other
brokers or dealers at a discount of up to $ per share from the initial price
to public. If all the shares are not sold at the initial price to public, the
representatives may change the offering price and the other selling terms.

ATMI, its directors and executive officers and two of the selling
stockholders have agreed with the underwriters not to dispose of or hedge any
of their common stock or securities convertible into or exchangeable for shares
of their common stock during the period from the date of this prospectus
continuing through the date 90 days after the date of this prospectus, except
with the prior written consent of Goldman, Sachs & Co. This agreement does not
apply to any sales by ATMI under its existing employee benefit plans. The
remaining selling stockholder has entered into a 45-day lock-up agreement with
the underwriters with respect to 1,100,922 shares of common stock.

46
<PAGE>

In connection with the offering, the underwriters may purchase and sell
shares of common stock in the open market. These transactions may include short
sales, stabilizing transactions and purchases to cover positions created by
short sales. Short sales involve the sale by the underwriters of a greater
number of shares than they are required to purchase in the offering.
Stabilizing transactions consist of bids or purchases made for the purpose of
preventing or retarding a decline in the market price of the common stock while
the offering is in progress.

The underwriters also may impose a penalty bid. This occurs when a
particular underwriter repays to the underwriters a portion of the underwriting
discount received by it because the representatives have repurchased shares
sold by or for the account of such underwriter in stabilizing or short covering
transactions.

These activities by the underwriters may stabilize, maintain or otherwise
affect the market price of the common stock. As a result, the price of the
common stock may be higher than the price that otherwise might exist in the
open market. If these activities are commenced, they may be discontinued by the
underwriters at any time. These transactions may be effected on the Nasdaq
National Market, in the over-the-counter market or otherwise.

ATMI is paying all expenses of the offering other than underwriting
discounts and commissions related to the sale of shares of common stock by the
selling stockholders. ATMI estimates that the total expenses of the offering,
excluding underwriting discounts and commissions, will be approximately
$600,000.

ATMI and the selling stockholders have agreed to indemnify the several
underwriters against some liabilities, including liabilities under the
Securities Act of 1933.

WHERE YOU CAN FIND MORE INFORMATION

We file annual, quarterly and current reports, proxy statements and other
documents with the Securities and Exchange Commission. You may read and copy
any document we file at the Commission's public reference rooms at Judiciary
Plaza, 450 Fifth Street, N.W., Washington, D.C. 20549, Seven World Trade
Center, Suite 1300, New York, New York 10048 and Citicorp Center, 500 West
Madison Street, Suite 1400, Chicago, Illinois 60661. Please call the Commission
at 1-800-SEC-0330 for further information on public reference rooms. Our
reports, proxy statements and other information filed with the Commission are
also available to the public from our web site at http://www.atmi.com or at the
Commission's web site at http://www.sec.gov.

This prospectus is part of a registration statement that we filed with the
Commission. The registration statement contains more information than this
prospectus regarding ATMI and its common stock, including certain exhibits and
schedules. You can get a copy of the registration statement from the sources
listed above.

The Commission allows us to "incorporate by reference" the information we
file with them, which means that we can disclose important information to you
by referring you to those documents. The information incorporated by reference
is considered to be part of this prospectus, and later information that we file
with the Commission will automatically update and supersede this information.
We incorporate by reference the documents listed below and any future filings
we will make with the Commission after the date we first filed the registration
statement of which this prospectus is a part under Section 13(a), 13(c), 14 or
15(d) of the Securities Exchange Act of 1934:

(1) Annual Report on Form 10-K for the year ended December 31, 1999 (File
No. 0-30130); and

47
<PAGE>

(2) The description of the common stock of ATMI's predecessor registrant,
Advanced Technology Materials, Inc., contained in its registration
statement on Form 8-A filed on October 23, 1993, which description was
amended on Form 8-A/A filed on November 11, 1993, and any amendment or
report filed to update this description.

You may request a copy of these documents, at no cost, by writing or
telephoning us at the following address:

ATMI, Inc.
7 Commerce Drive
Danbury, Connecticut 06810
Attn: Dean Hamilton
(203) 794-1100

LEGAL MATTERS

Shipman & Goodwin LLP, Hartford, Connecticut, is giving us its opinion on
the validity of the shares being offered. As of the date of this prospectus,
lawyers employed at Shipman & Goodwin owned 7,000 shares of our common stock.
Legal matters will be passed upon for the underwriters by Ropes & Gray, Boston,
Massachusetts.

EXPERTS

The consolidated financial statements and related schedule of ATMI, Inc. at
December 31, 1999 and 1998 and for each of the three years in the period ended
December 31, 1999, appearing in this Prospectus and Registration Statement have
been audited by Ernst & Young LLP, independent auditors, as set forth in their
report appearing elsewhere herein which, as to 1998 is based in part on the
report of Arthur Andersen LLP and the reports of Rath, Anders, Dr. Wanner and
Partner, and as to 1997 is based in part on the report of Deloitte & Touche
LLP. The financial statements referred to above are included in reliance upon
such reports given on the authority of such firms as experts in accounting and
auditing.

48
<PAGE>

ATMI, INC.

INDEX TO CONSOLIDATED FINANCIAL STATEMENTS AND
FINANCIAL STATEMENT SCHEDULE

<TABLE>
<CAPTION>
Page
----
<S> <C>
Report of Ernst & Young LLP............................................... F-2
Report of Deloitte & Touche, LLP.......................................... F-3
Report of Arthur Andersen LLP............................................. F-4
Reports of Rath, Anders, Dr. Wanner and Partner (GbR)..................... F-5
Audited Financial Statements and Schedule
Consolidated Balance Sheets--December 31, 1998 and 1999................. F-7
Consolidated Statements of Income for the years ended December 31, 1997,
1998, and 1999......................................................... F-8
Consolidated Statements of Stockholders' Equity for the years ended
December 31, 1997, 1998, and 1999...................................... F-9
Consolidated Statements of Cash Flows for the years ended December 31,
1997,
1998, and 1999......................................................... F-10
Notes to Consolidated Financial Statements.............................. F-11
Schedule II--Valuation and Qualifying Accounts.......................... F-28
</TABLE>

F-1
<PAGE>

REPORT OF INDEPENDENT AUDITORS

The Board of Directors and Stockholders of
ATMI, Inc.

We have audited the consolidated balance sheets of ATMI, Inc. as of
December 31, 1998 and 1999, and the related consolidated statements of income,
stockholders' equity and cash flows for each of the three years in the period
ended December 31, 1999. Our audits also included the financial statement
schedule listed in the Index. These consolidated financial statements are the
responsibility of the management of ATMI, Inc. Our responsibility is to express
an opinion on these consolidated financial statements and schedule based on our
audits. We did not audit the December 31, 1998 financial statements or
Valuation and Qualifying Accounts Schedule Data of MST Analytics, Inc. ("MST"),
a wholly-owned subsidiary, which statements reflect total assets and total
revenues constituting 6% and 12%, respectively, of the related consolidated
totals at and for the year ended December 31, 1998. Nor did we audit the March
31, 1998 financial statements of NOW Technologies, Inc. ("NOW"), a wholly owned
subsidiary, which statements reflect total revenues constituting 8% of the
related consolidated totals for the year ended March 31, 1998 (which was
combined with the accounts of ATMI, Inc. for the year ended December 31, 1997).
Those statements were audited by other auditors whose reports have been
furnished to us, and our opinion, insofar as it relates to data included for
MST and NOW, for the periods indicated, is based solely on the reports of such
other auditors.

We conducted our audits in accordance with auditing standards generally
accepted in the United States. 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. An audit also includes assessing the accounting principles used and
significant estimates made by management, as well as evaluating the overall
financial statement presentation. We believe that our audits and the reports of
the other auditors provide a reasonable basis for our opinion.

In our opinion, based on our audits and the reports of other auditors, the
consolidated financial statements referred to above present fairly, in all
material respects, the consolidated financial position of ATMI, Inc. at
December 31, 1998 and 1999, and the consolidated results of its operations and
its cash flows for each of the three years in the period ended December 31,
1999 in conformity with accounting principles generally accepted in the United
States. Also, in our opinion, the related consolidated financial statement
schedule, when considered in relation to the basic consolidated financial
statements taken as a whole, presents fairly in all material respects the
information set forth therein.

Ernst & Young LLP

Stamford, Connecticut
February 7, 2000

F-2
<PAGE>

INDEPENDENT AUDITORS' REPORT

Board of Directors
NOW Technologies, Inc. and Subsidiaries
Bloomington, Minnesota

We have audited the consolidated statements of income, stockholders' equity
and cash flows (not presented herein) of NOW Technologies, Inc. and
Subsidiaries (the Company) for the year ended March 31, 1998. These
consolidated financial statements are the responsibility of the Company's
management. Our responsibility is to express an opinion on these financial
statements based on our audit.

We conducted our audit 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. An audit
also includes assessing the accounting principles used and significant
estimates made by management, as well as evaluating the overall financial
statement presentation. We believe that our audit provides a reasonable basis
for our opinion.

In our opinion, such consolidated financial statements present fairly, in
all material respects, the results of the Company's operations and its cash
flows for the year ended March 31, 1998, in conformity with generally accepted
accounting principles.

Deloitte & Touche, LLP

Minneapolis, Minnesota
May 1, 1998

F-3
<PAGE>

REPORT OF INDEPENDENT PUBLIC ACCOUNTANTS

To the Board of Directors of
MST Analytics, Inc.

We have audited the consolidated balance sheet of MST ANALYTICS, INC. (a
Delaware corporation) AND SUBSIDIARIES as of December 31, 1998, and the related
consolidated statements of operations, stockholders' equity and cash flows for
the year then ended. These financial statements are the responsibility of the
Company's management. Our responsibility is to express an opinion on these
financial statements based on our audit. We did not audit the financial
statements of MST Micro-Sensor-Technologie GmbH, Hohenschaftlarn and Sensoric
Gesellschaft fur angewandte Elektrochemie mbh & Co. KG, Hohenschaftlarn, wholly
and majority-owned subsidiaries, respectively, which statements reflect total
assets and total revenues of 55% and 47%, respectively, of the related
consolidated totals. Those statements were audited by other auditors whose
report has been furnished to us, and our opinion, insofar as it relates to the
amounts included for those entities, is solely based on the report of the other
auditors.

In our opinion, based on our audit and the report of other auditors, the
consolidated financial statements referred to above present fairly, in all
material respects, the financial position of MST Analytics, Inc. and
Subsidiaries as of December 31, 1998, and the results of their operations and
their cash flows for the year then ended, in conformity with generally accepted
accounting principles.

Arthur Andersen LLP

Chicago, Illinois
May 28, 1999

F-4
<PAGE>

OPINION

MST Micro-Sensor-Technologie GmbH
Hohenschaftlarn, Germany

We have conducted a full audit of MST Micro-Sensor-Technologie GmbH,
Hohenschaftlarn, (in the following called "MST" or "Company"), expressed in
Deutsche Mark (DM), as of December 31, 1998.

(1) These financial statements are the responsibility of the Company's
management. Our responsibility is to express an opinion on these
financial statements based on our audit.

(2) We have conducted our audit in accordance with generally accepted
auditing standards in the United States. These standards require that
we plan and perform the audit to obtain reasonable assurance about
whether the financial statements are free of material misstatements.
An audit includes examining, on a test basis, evidence supporting the
amounts and disclosures in the financial statements. An audit also
includes assessing the accounting principles used and significant
estimates made by management, as well as evaluating the overall
financial statement presentation. We believe that our audit provides a
reasonable basis for our opinion.

(3) The reporting package does not present all disclosures required under
US-GAAP, e.g. no cash flow statement and no tax rationalization form
have been prepared.

(4) On the basis of our audit we certify that the documents attached to
this clearance have been issued in compliance with the methods and
principles accepted by US-GAAP.

Munich, January 22, 1999
Rath, Anders, Dr. Wanner & Partner

Dipl.-Kfm. Kabisch Dipl.-Kfm. Metzler
Vereidigter Buchprufer Wirtschaftsprufer

F-5
<PAGE>

OPINION

Sensoric Gesellschaft fur angewandte
Elektrochemie mbh Co. KG
Hohenschaftlarn

We have conducted a full audit of Sensoric Gesellschaft fur angewandte
Elektrochemie mbh & Co. KG, Hohenschaftlarn, (in the following called
"Sensoric" or "Company"), expressed in Deutsche Mark (DM), as of December 31,
1998.

(1) These financial statements are the responsibility of the Company's
management. Our responsibility is to express an opinion on these
financial statements based on our audit.

(3) The reporting package does not present all disclosures required under
US-GAAP, e.g. no cash flow statement and no tax rationalization form
have been prepared.

(4) On the basis of our audit we certify that the documents attached to
this clearance have been issued in compliance with the methods and
principles accepted by US-GAAP.

Munich, January 22, 1999
Rath, Anders, Dr. Wanner & Partner

Dipl.-Kfm. Kabisch Dipl.-Kfm. Metzler
Vereidigter Buchprufer Wirtschaftsprufer

F-6
<PAGE>

ATMI, INC.

CONSOLIDATED BALANCE SHEETS

(in thousands, except per share data)

<TABLE>
<CAPTION>
December 31,
------------------
1998 1999
-------- --------
<S> <C> <C>
ASSETS
Current assets:
Cash and cash equivalents (Note 1)........................ $ 21,618 $ 31,619
Marketable securities (Notes 1 and 2)..................... 64,551 60,555
Accounts receivable, net of allowance for doubtful
accounts of
$959 in 1998, and $1,366 in 1999 (Note 3)................ 25,708 41,989
Inventories (Notes 1 and 4)............................... 19,216 21,733
Deferred income taxes (Note 8)............................ 2,756 5,277
Other..................................................... 7,717 6,256
-------- --------
Total current assets.................................... 141,566 167,429
Property, plant and equipment, net (Notes 1 and 5).......... 54,683 54,675
Deferred income taxes (Note 8).............................. 48 2,090
Goodwill and other long-term assets, net (Notes 1 and 11)... 12,355 8,462
-------- --------
$208,652 $232,656
======== ========
LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities:
Accounts payable.......................................... $ 9,287 $ 10,971
Accrued liabilities....................................... 9,976 10,146
Accrued salaries and related benefits..................... 3,547 9,185
Loans, notes and bonds payable, current portion (Note 6).. 9,396 4,964
Capital lease obligations, current portion (Note 7)....... 2,493 1,936
Income taxes payable (Note 8)............................. 1,972 4,592
Deferred income taxes (Note 8)............................ 957 4,436
-------- --------
Total current liabilities............................... 37,628 46,230
Loans, notes and bonds payable, less current portion (Note
6)......................................................... 8,813 4,448
Capital lease obligations, less current portion (Note 7).... 3,746 1,832
Deferred income taxes (Note 8).............................. 4,611 3,754
Other long-term liabilities................................. 288 478
Minority interest........................................... 846 1,109
Stockholders' equity (Note 10):
Preferred stock, par value $.01: 2,000 shares authorized;
none issued and outstanding.............................. -- --
Common stock, par value $.01: 50,000 shares authorized;
issued, 27,484 in 1998 and 27,774 in 1999................ 275 278
Additional paid-in capital................................ 118,516 122,536
Retained earnings......................................... 35,082 45,465
Accumulated other comprehensive income (loss)............. (1,153) 6,526
-------- --------
Total stockholders' equity.............................. 152,720 174,805
-------- --------
$208,652 $232,656
======== ========
</TABLE>

See accompanying notes.

F-7
<PAGE>

ATMI, INC.

CONSOLIDATED STATEMENTS OF INCOME

(in thousands, except per share data)

<TABLE>
<CAPTION>
Year Ended December 31,
----------------------------
1997 1998 1999
-------- -------- --------
<S> <C> <C> <C>
Revenues (Notes 1 and 15)....................... $192,012 $165,106 $196,236
Cost of revenues................................ 92,561 83,419 92,970
-------- -------- --------
Gross profit.................................... 99,451 81,687 103,266
Operating expenses:
Research and development (Note 1)............. 14,336 16,630 18,359
Selling, general and administrative (Note
13).......................................... 60,593 56,925 60,305
Merger costs and related expenses (Note 11)... 9,000 1,700 9,914
-------- -------- --------
83,929 75,255 88,578
-------- -------- --------
Operating income................................ 15,522 6,432 14,688
Interest income................................. 1,732 4,210 4,384
Interest expense (Note 6)....................... (2,609) (1,723) (1,267)
Other income, net............................... 340 539 724
-------- -------- --------
Income before taxes and minority interest....... 14,985 9,458 18,529
Income taxes (Note 8)........................... 8,588 4,412 7,720
-------- -------- --------
Income before minority interest................. 6,397 5,046 10,809
Minority interest............................... (2) (111) (263)
-------- -------- --------
Net income (Note 15)............................ $ 6,395 $ 4,935 $ 10,546
======== ======== ========
Net income per share--basic (Notes 1 and 10).... $ 0.27 $ 0.19 $ 0.40
======== ======== ========
Net income per share--assuming dilution (Notes 1
and 10)........................................ $ 0.25 $ 0.18 $ 0.37
======== ======== ========
Weighted average shares outstanding--basic
(Notes 1 and 10)............................... 23,617 25,645 26,440
======== ======== ========
Weighted average shares outstanding--assuming
dilution (Notes 1 and 10)...................... 25,660 27,423 28,319
======== ======== ========
</TABLE>

See accompanying notes.

F-8
<PAGE>

ATMI, INC.

CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY

(in thousands)

<TABLE>
<CAPTION>
Accumulated
Additional Other
Common Paid-in Retained Comprehensive
Stock Capital Earnings Income Total
------ ---------- -------- ------------- --------
<S> <C> <C> <C> <C> <C>
Balance at December 31,
1996..................... $239 $ 41,438 $24,450 $ (78) $ 66,049
Issuance of 83 common
shares pursuant to the
exercise of employee
stock options............ -- 454 -- -- 454
Issuance of 151 common
shares pursuant to the
exercise of warrants..... 2 1,688 -- -- 1,690
Issuance of common shares
to pooled entity......... 10 4,284 -- -- 4,294
Issuance of common and
preferred shares by
pooled entity............ -- 5,046 -- -- 5,046
Distributions to
stockholders............. -- -- (199) -- (199)
Compensation for the
issuance of common
shares................... -- 272 -- -- 272
Tax benefit related to
nonqualified stock
options.................. -- 678 -- -- 678
Net income................ 6,395 6,395
Cumulative translation
adjustment............... -- -- -- (1,376) (1,376)
--------
Comprehensive income...... 5,019
---- -------- ------- ------ --------
Balance at December 31,
1997..................... 251 53,860 30,646 (1,454) 83,303
---- -------- ------- ------ --------
Issuance of 159 common
shares pursuant to the
exercise of employee
stock options............ 1 782 -- -- 783
Sale of 2,257 common
shares, net of issuance
costs of $4,161.......... 23 62,403 -- -- 62,426
Compensation for the
issuance of common
shares................... -- 372 -- -- 372
Tax benefit related to
nonqualified stock
options.................. -- 1,099 -- -- 1,099
Distributions to
stockholders............. -- -- (397) -- (397)
Adjustment to reflect
change in pooled entity
fiscal year.............. -- -- (102) -- (102)
Net income................ -- -- 4,935 -- 4,935
Unrealized loss on
available-for-sale
securities (net of tax
benefit of $281)......... -- -- -- (500) (500)
Cumulative translation
adjustment............... -- -- -- 801 801
--------
Comprehensive income...... 5,236
---- -------- ------- ------ --------
Balance at December 31,
1998..................... 275 118,516 35,082 (1,153) 152,720
---- -------- ------- ------ --------
Issuance of 204 common
shares pursuant to the
exercise of employee
stock options............ 2 1,046 -- -- 1,048
Issuance of 20 common
shares pursuant to the
exercise of warrants..... -- 222 -- -- 222
Issuance of 64 common
shares pursuant to the
employee stock purchase
plan..................... 1 952 -- -- 953
Compensation for the
issuance of common
shares................... -- 426 -- -- 426
Tax benefit related to
nonqualified stock
options.................. -- 1,374 -- -- 1,374
Adjustment to reflect
change in pooled entity
fiscal year.............. -- -- (163) -- (163)
Net income................ -- -- 10,546 -- 10,546
Unrealized gain on
available-for-sale
securities (net of tax
provision of $4,141)..... -- -- -- 7,860 7,860
Cumulative translation
adjustment............... -- -- -- (181) (181)
--------
Comprehensive income...... 18,225
---- -------- ------- ------ --------
Balance at December 31,
1999..................... $278 $122,536 $45,465 $6,526 $174,805
---- -------- ------- ------ --------
</TABLE>

See accompanying notes.

F-9
<PAGE>

ATMI, INC.

CONSOLIDATED STATEMENTS OF CASH FLOWS

(in thousands, except per share data)

<TABLE>
<CAPTION>
Year Ended December 31,
----------------------------
1997 1998 1999
-------- -------- --------
<S> <C> <C> <C>
Operating activities
Net income...................................... $ 6,395 $ 4,935 $ 10,546
Adjustments to reconcile net income to net cash
provided by operating activities:
Depreciation and amortization.................. 7,957 9,900 10,868
Write-down of goodwill......................... -- -- 3,386
Stock option compensation...................... 272 372 426
Effect of change of fiscal year of pooled
entity........................................ -- (102) (163)
Provision for bad debt......................... 1,251 399 587
Deferred income taxes.......................... 2,369 (1,891) (6,677)
Tax benefit of nonqualified stock options...... 678 1,099 1,374
Minority interest in net earnings of
subsidiaries.................................. 2 111 263
Changes in operating assets and liabilities
(Increase) decrease in accounts receivable.... (11,624) 10,667 (16,868)
(Increase) in inventory....................... (4,085) (796) (2,517)
(Increase) decrease in other assets........... (2,990) (4,394) 1,330
Increase (decrease) in accounts payable....... (628) (1,187) 1,684
Increase (decrease) in accrued expenses....... 4,055 (5,156) 5,808
Increase (decrease) in other liabilities...... 473 (672) 3,017
-------- -------- --------
Total adjustments........................... (2,270) 8,350 2,518
-------- -------- --------
Net cash provided by operating activities... 4,125 13,285 13,064
-------- -------- --------

Investing activities
Capital expenditures............................ (9,084) (15,023) (10,222)
Long-term investment............................ (250) -- --
Sale (purchase) of marketable securities, net... 777 (47,871) 16,278
Payments for acquisitions....................... (5,551) -- --
Proceeds from sale of assets.................... -- 199 --
-------- -------- --------
Net cash provided (used) by investing
activities................................. (14,108) (62,695) 6,056
-------- -------- --------

Financing activities
Borrowings from loans, notes, and bonds
payable........................................ 4,630 2,232 303
Payments on loans, notes, and bonds payable..... (4,411) (6,747) (9,100)
Distribution to stockholders.................... (199) (397) --
Payments on capital lease obligations........... (3,125) (2,831) (2,471)
Proceeds from sale of common stock, net......... -- 62,426 --
Proceeds from sale of common and preferred stock
by pooled entities............................. 8,549 -- --
Investment by minority stockholder.............. 251 -- --
Proceeds from exercise of stock options and
warrants....................................... 2,144 783 2,223
-------- -------- --------
Net cash provided (used) by financing
activities................................. 7,839 55,466 (9,045)
-------- -------- --------
Effects of exchange rate changes on cash........ (142) 120 (74)
-------- -------- --------
Net increase (decrease) in cash and cash
equivalents.................................... (2,286) 6,176 10,001
Cash and cash equivalents, beginning of year.... 17,728 15,442 21,618
-------- -------- --------
Cash and cash equivalents, end of year.......... $ 15,442 $ 21,618 $ 31,619
======== ======== ========

Disclosure of noncash financing activities
Conversion of note payable to preferred stock by
pooled entity.................................. $ 685 -- --
======== ======== ========
</TABLE>

See accompanying notes.

F-10
<PAGE>

ATMI, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS

1. Summary of Significant Accounting Policies

Basis of Presentation

The consolidated financial statements include the accounts of ATMI, Inc.
and its majority-owned subsidiaries, after elimination of intercompany accounts
and transactions.

Certain amounts have been reclassified to conform to current year
presentation.

Company's Activities

ATMI, Inc. together with its subsidiaries (the "Company") is a leading
supplier of materials, equipment and related services used in the manufacture
of semiconductor devices. The Company targets specialty materials used in
front-end semiconductor manufacture. The Company provides:

. a broad range of ultrahigh-purity semiconductor materials;

. semiconductor materials packaging and delivery systems;

. sensors for the workplace and environment that detect materials as they
move through the workplace;

. point-of-use environmental equipment that abates materials; and

. specialty thin film deposition services that provide coated wafers
directly to customers.

Revenue Recognition

Revenues are recognized upon the shipment of goods.

Use of Estimates

The preparation of the financial statements in conformity with accounting
principles generally accepted in the United States requires management to make
estimates and assumptions that affect the amounts reported in the financial
statements and accompanying notes. Actual results may differ from those
estimates.

Research and Development

Research and development costs, including materials, labor, and overhead
related to self-funded projects, are expensed as incurred.

Marketable Securities and Investments

Highly liquid investments with maturities of three months or less, when
purchased, are classified as cash and cash equivalents. Investments with
maturities greater than three months are classified as marketable securities.

In connection with the Company's strategic alliances and research and
development activities, it has acquired equity securities of certain of its
alliance partners.

The Company accounts for investments in accordance with SFAS No. 115,
"Accounting for Certain Investments in Debt and Equity Securities." The
Company's policy, except for its equity

F-11
<PAGE>

ATMI, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(Continued)

1. Summary of Significant Accounting Policies (continued)

investments in alliance partners, is to protect the value of its investments
portfolio and to minimize principal risk by earning returns based on current
interest rates. All of the Company's marketable securities are classified as
available-for-sale as of the balance sheet date and are reported at fair value,
based on quoted market prices, with unrealized gains and losses recorded in
accumulated other comprehensive income, net of tax. The cost of securities sold
is based on the specific identification method. Interest on these securities is
accrued and included in interest income.

Management determines the classification of marketable debt securities at
the time of purchase and reevaluates such designation as of each balance sheet
date.

Inventories

Inventories are stated at the lower of cost or market using the first-in,
first-out (FIFO) method.

Property, Plant and Equipment

Property and equipment is stated at cost. Depreciation and amortization of
property, plant and equipment is computed using the straight-line method over
the estimated useful lives of the assets, which vary from three to thirty-five
years.

Foreign Currency Translation

Adjustments relating to the translation of foreign currency to U.S. dollars
are reported as a separate component of accumulated other comprehensive income.
Gains or losses resulting from foreign currency transactions are included in
other income (expense) and have been immaterial.

Taxes

The Company accounts for income taxes in accordance with the liability
method. Under this method, deferred tax assets and liabilities are determined
based upon differences between financial reporting and the tax basis of assets
and liabilities and are measured using the enacted tax rates and laws that are
expected to be in effect when the differences are expected to reverse.

Fair Values of Financial Instruments

The Company's financial instruments include cash and cash equivalents,
marketable securities, accounts receivable, and debt. Marketable securities are
accounted for at fair value. All other financial instruments are accounted for
on an historical cost basis which, due to the nature of these instruments,
approximates fair value at the balance sheet dates.

Long-Lived Assets

The Company reviews on a periodic basis the value of its long-lived assets
to determine whether an impairment exists. In connection with the acquisition
of Delatech, the Company recorded a charge of $3.4 million associated with the
impairment of goodwill related to an existing EcoSys product line (see Note
11). This charge was based on the estimate of future cash flows on a discounted
basis compared with the carrying value of the goodwill. Goodwill of $7.8
million and $3.7 million at December 31, 1998 and 1999 is amortized over
periods of ten to twenty years and is stated net of accumulated amortization of
$1.5 million and $2.2 million at December 31, 1998 and 1999, respectively.

F-12
<PAGE>

ATMI, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(Continued)

1. Summary of Significant Accounting Policies (continued)

Stock Based Compensation

The Company accounts for employee stock compensation plans in accordance
with Accounting Principle Board (APB) Opinion No. 25, "Accounting for Stock
Issued to Employees." Under APB No. 25, compensation cost is the excess, if
any, of the quoted market price of the Company's common stock at the grant date
over the amount the employee must pay to acquire the common stock. The Company
has elected to continue to account for its employee stock compensation plans
under APB No. 25. Pro forma disclosures of net income, net income per share-
basic and net income per share- assuming dilution, as if the fair value based
method of accounting had been applied, are presented in Note 10.

Per Share Data

Basic and diluted earnings per share are calculated in accordance with FASB
Statement No. 128, "Earnings Per Share".

Recent Accounting Pronouncements

In December 1999, the SEC issued Staff Accounting Bulletin ("SAB") 101,
"Revenue Recognition," which provides guidance on the recognition,
presentation, and disclosure of revenue in financial statements filed with the
SEC. SAB 101 outlines the basic criteria that must be met to recognize revenue
and provides guidance for disclosure related to revenue recognition policies.
At this time, the Company is still assessing the impact of SAB 101 on its
financial position and results of operations.

2. Marketable Securities

Marketable securities are comprised of the following at December 31, 1998
(in thousands):

<TABLE>
<CAPTION>
Gross
Unrealized Fair
Cost Loss Value
------- ---------- -------
<S> <C> <C> <C>
Corporate obligations............................ $49,563 $ -- $49,563
U.S. Government obligations...................... 8,695 -- 8,695
Certificates of deposit.......................... 4,887 -- 4,887
------- ------- -------
Total debt securities.......................... 63,145 -- 63,145
Common stock..................................... 2,187 (781) 1,406
------- ------- -------
Total marketable securities.................... $65,332 $ (781) $64,551
======= ======= =======

Marketable securities are comprised of the following at December 31, 1999
(in thousands):

<CAPTION>
Gross
Unrealized Fair
Cost Gain Value
------- ---------- -------
<S> <C> <C> <C>
Corporate obligations............................ $36,887 $ -- $36,887
U.S. Government obligations...................... 3,969 -- 3,969
Certificates of deposit.......................... 6,011 -- 6,011
------- ------- -------
Total debt securities.......................... 46,867 -- 46,867
Common stock..................................... 2,187 11,501 13,688
------- ------- -------
Total marketable securities.................... $49,054 $11,501 $60,555
======= ======= =======
</TABLE>

All of the Company's marketable debt securities have maturities of less
than two years.

F-13
<PAGE>

ATMI, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(Continued)

3. Accounts Receivable

Credit is extended to commercial customers based on an evaluation of their
financial condition, and collateral is not generally required. The evaluation
of financial condition is performed to reduce the risk of loss. The Company has
not experienced any material losses due to uncollectible accounts receivable.
Certain transactions with foreign customers are supported by letters of credit.
The Company maintains an allowance for doubtful accounts at a level that
management believes is sufficient to cover potential credit losses.

Amounts due from various agencies of the U.S. Government were approximately
$2.1 million and $2.7 million at December 31, 1998 and 1999, respectively.

4. Inventories

Inventories are comprised of the following (in thousands):

<TABLE>
<CAPTION>
December 31,
----------------
1998 1999
------- -------
<S> <C> <C>
Raw materials.............................................. $14,335 $16,088
Work in process............................................ 2,392 3,059
Finished goods............................................. 4,350 4,115
------- -------
21,077 23,262
Obsolescence reserve....................................... (1,861) (1,529)
------- -------
$19,216 $21,733
======= =======
</TABLE>

5. Property, Plant and Equipment

Property, plant and equipment is comprised of the following (in thousands):

<TABLE>
<CAPTION>
December 31,
------------------
1998 1999
-------- --------
<S> <C> <C>
Land..................................................... $ 1,944 $ 2,738
Buildings................................................ 10,522 9,875
Machinery and equipment.................................. 63,624 70,691
Furniture and fixtures................................... 5,657 6,839
Leasehold improvements................................... 8,094 9,287
-------- --------
89,841 99,430
Accumulated depreciation and amortization................ (35,158) (44,755)
-------- --------
$ 54,683 $ 54,675
======== ========
</TABLE>

Depreciation expense for the years ended December 31, 1997, 1998, and 1999,
was $7.4 million, $9.1 million and $10.2 million, respectively.

F-14
<PAGE>

ATMI, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(Continued)

6. Loans, Notes and Bonds Payable

Loans, notes and bonds payable consist of the following (in thousands):

<TABLE>
<CAPTION>
December 31,
----------------
1998 1999
------- -------
<S> <C> <C>
Note payable bearing interest at 8.25%, due in three annual
installments beginning January 1, 1999..................... $ 2,000 $ 1,333
Term loans with Connecticut state agency, bearing interest
ranging between 5%-5.75%, due between January 2000 and June
2002....................................................... 2,212 1,490
Credit lines with commercial banks, bearing interest ranging
between 6.50%-8.75% available through February 2000........ 2,376 940
Notes payable primarily with commercial banks and leasing
companies, bearing interest ranging between 2.5%-6.0%, due
between April 1998 and September 2008...................... 7,466 3,349
Mortgages payable, bearing interest at 8.63%, due November
2016....................................................... 1,455 --
City of Bloomington, Minnesota Industrial Revenue Bond,
interest rate is variable (4.4% and 4.2% at December 31,
1998 and 1999), quarterly payments of $0.1 million, due
September 2005............................................. 2,700 2,300
------- -------
18,209 9,412
Less current portion........................................ (9,396) (4,964)
------- -------
$ 8,813 $ 4,448
======= =======
</TABLE>

The approximate aggregate debt maturities are as follows as of December 31,
1999 (in thousands):

<TABLE>
<S> <C>
2000.................................. $3,064
2001.................................. 2,735
2002.................................. 1,800
2003.................................. 672
2004.................................. 522
Thereafter............................ 619
------
$9,412
======
</TABLE>

The balance of loans and notes payable at December 31, 1998 and 1999,
respectively include amounts due in foreign currencies as follows: Belgian
Francs 68,499,000 and 64,046,000 ($1,994,000 and $1,595,000) and Deutschmarks
7,498,000 and 4,486,000 ($4,502,000 and $2,305,000).

The term loans are collateralized by various equipment, leasehold
improvements and renovations in the Company's Connecticut facility. The
mortgages are collateralized by the building at the Company's Napa, California
facility. The majority of the Company's notes payable are secured by the
related real property or equipment. The Company's credit lines are secured by
substantially all the assets of certain of the Company's subsidiaries and have
available borrowing capacity approximating $1.8 million at December 31, 1999.
The Company is in compliance with the credit line and notes payable covenants.

The bondholders may tender the City of Bloomington, Minnesota bonds at any
time for the principal amount plus accrued interest. As a result, they have
been classified as a current liability.

F-15
<PAGE>

ATMI, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(Continued)

6. Loans, Notes and Bonds Payable (continued)

The Company has the option to convert the bonds to a fixed rate provided all
bonds can be remarketed at the fixed rate. The first fixed rate optional
redemption date would be July 1 of the year that is halfway between the
conversion date and July 1, 2005. If redeemed, the Company must pay 102% and
101% of bond principal in the first and second years following the first fixed
rate optional redemption date, respectively. Prior to conversion to a fixed
rate, the Company has the option to redeem the bonds without premium.

Interest paid was $2.8 million, $2.3 million, and $1.3 million, for the
years ended December 31, 1997, 1998, and 1999, respectively.

Certain of the Company's subsidiaries' financing agreements contain
limitations or prohibitions on the payment of dividends without the lender's
consent or in conjunction with the subsidiary's failure to comply with various
financial covenants. The Company has never declared or paid cash dividends on
its capital stock. The Company does not anticipate paying any cash dividends in
the foreseeable future.

7. Leases

The Company is obligated under capital leases for certain machinery and
equipment that expire at various dates during the next five years. The gross
amount of machinery and equipment under the capital leases and the related
accumulated depreciation were as follows (in thousands):

<TABLE>
<CAPTION>
December 31,
----------------
1998 1999
------- -------
<S> <C> <C>
Machinery and equipment.................................... $12,269 $10,380
Accumulated depreciation................................... (3,109) (3,173)
------- -------
$ 9,160 $ 7,207
======= =======
</TABLE>

The following is a schedule of future minimum lease payments for capital
leases as of December 31, 1999 (in thousands):

<TABLE>
<S> <C>
2000............................................................ $ 2,175
2001............................................................ 1,560
2002............................................................ 365
-------
Total lease payments.......................................... 4,100
Less amount representing interest............................... (332)
-------
Present value of net capital lease payments..................... 3,768
Less current portion............................................ (1,936)
-------
Long-term portion............................................. $ 1,832
=======
</TABLE>

The Company leases office and manufacturing facilities, and certain
manufacturing equipment under several operating leases expiring between 2000
and 2005. Rental expense was $4.6 million, $5.0 million, and $4.7 million, for
the years ended December 31, 1997, 1998 and 1999, respectively.

F-16
<PAGE>

ATMI, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(Continued)

7. Leases (continued)

The following is a schedule of future minimum lease payments for operating
leases as of December 31, 1999 (in thousands):

<TABLE>
<CAPTION>
Operating
Leases
---------
<S> <C>
2000........................................................... $ 3,393
2001........................................................... 2,495
2002........................................................... 1,703
2003........................................................... 994
2004........................................................... 878
Thereafter..................................................... 594
-------
Total minimum lease payments................................. $10,057
=======
</TABLE>

8. Income Taxes

Pretax income was taxed in the following jurisdictions (in thousands):

<TABLE>
<CAPTION>
Year Ended December 31,
-------------------------
1997 1998 1999
-------- ------- --------
<S> <C> <C> <C>
Domestic........................................... $ 13,677 $ 5,989 $ 15,672
Foreign............................................ 1,306 3,358 2,594
-------- ------- --------
Total pretax income.............................. $ 14,983 $ 9,347 $ 18,266
======== ======= ========
</TABLE>

Significant components of the provision for income taxes for the periods
presented are as follows (in thousands):

<TABLE>
<CAPTION>
December 31,
-----------------------
1997 1998 1999
------ ------- -------
<S> <C> <C> <C>
Current:
Federal........................................... $5,305 $ 4,539 $11,811
State............................................. 740 1,116 1,635
Foreign........................................... 174 648 951
------ ------- -------
Total current................................... 6,219 6,303 14,397
------ ------- -------
Deferred:
Federal........................................... 1,896 (1,816) (5,901)
State............................................. 321 (536) (746)
Foreign........................................... 152 461 (30)
------ ------- -------
Total deferred.................................. 2,369 (1,891) (6,677)
------ ------- -------
$8,588 $ 4,412 $ 7,720
====== ======= =======
</TABLE>

F-17
<PAGE>

ATMI, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(Continued)

8. Income Taxes (continued)

Significant components of the Company's deferred tax assets and liabilities
are as follows (in thousands):

<TABLE>
<CAPTION>
December 31,
----------------
1998 1999
------- -------
<S> <C> <C>
Deferred tax assets:
Accrued liabilities..................................... $ 1,234 $ 3,565
Inventory reserves...................................... 1,183 1,713
Net operating loss and tax credit carryforwards......... 2,045 1,823
Other, net.............................................. 496 266
------- -------
4,958 7,367
Valuation allowance....................................... (2,154) --
------- -------
2,804 7,367
Deferred tax liabilities:
Depreciation and amortization........................... (4,614) (3,736)
Unrealized gain on marketable securities................ -- (4,141)
Other, net.............................................. (954) (313)
------- -------
(5,568) (8,190)
------- -------
Net deferred tax liabilities.............................. $(2,764) $ (823)
======= =======
</TABLE>

The valuation allowance was eliminated as a result of changes in estimates
regarding the realizability of net operating loss and tax credit carryforwards
of certain acquired companies.

As of December 31, 1999, the Company has federal net operating loss
carryforwards of $4.6 million attributable to certain acquired companies and
tax credit carryforwards of $0.2 million. The net operating loss and tax credit
carryforwards will expire at various dates beginning in 2007 through 2019, if
not utilized. Utilization of the net operating losses and credits may be
subject to a substantial annual limitation due to the "change in ownership"
provisions of the Internal Revenue Code of 1986 and similar state provisions.

Income taxes paid for the years ended December 31, 1997, 1998, and 1999
were $6.1 million, $9.4 million and $9.2 million, respectively.

The reconciliation of income tax computed at the U.S. federal statutory tax
rate to the Company's tax expense is (in thousands):

<TABLE>
<CAPTION>
For the Year Ended December 31,
-----------------------------------
1997 1998 1999
---------- ---------- -----------
<S> <C> <C> <C>
U.S. statutory rate................... $ 5,094 $ 3,178 $ 6,393
State income taxes.................... 662 266 657
Foreign income taxes.................. (24) 228 (162)
Effect of nondeductible acquisition
expenses............................. 3,548 599 1,851
Net operating loss carryforward
utilization.......................... (296) -- --
Foreign sales corporation benefit..... -- (324) (773)
Reversal of valuation allowance....... (954) 855 (2,154)
Tax liabilities accrued............... -- -- 1,511
Other, net............................ 558 (390) 397
---------- ---------- -----------
$ 8,588 $ 4,412 $ 7,720
========== ========== ===========
</TABLE>

F-18
<PAGE>

ATMI, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(Continued)

8. Income Taxes (continued)

South Korea has granted the Company a five year full income tax exemption,
which expires in 2003, and an additional three year 50% exemption, which
expires in 2006. The effect of the tax exemption was to reduce income tax
expense by $0.1 million and $0.2 million for the years ended December 31, 1998
and 1999, respectively.

The former securityholders of the ADCS Group have agreed to indemnify the
Company against losses arising out of certain tax matters. As security for
these tax matters, the former securityholders of the ADCS Group have delivered
700,000 shares of the Company's common stock which they received into escrow
(see Note 11). While the possible exposures are difficult to quantify, the
Company believes that, regardless of the probability that liabilities arise,
the potential exposures range from $0 to $22 million depending on the tax
matter. Although the former securityholders of the ADCS Group have agreed to
indemnify the Company against losses arising out of such tax matters, any
assessments, if ultimately determined against the Company, would result in a
charge to the Company's results of operations. During the second quarter 1999,
the Company was notified by the Internal Revenue Service of an assessment of
$2.1 million for certain tax matters. The Company believes that such assessment
is without merit and intends to vigorously defend its position in these tax
matters.

9. Profit Sharing Plan

The Company maintains a 401(k) profit sharing plan (the "Plan") covering
substantially all of its employees and is subject to the provisions of the
Employee Retirement Income Security Act of 1974. The Company's matching
contributions are discretionary by plan year and were $0.1 million, $0.1
million and $0.4 million for 1997, 1998 and 1999, respectively.

10. Stockholders' Equity

In March 1998, the Company completed a registered underwritten public
offering of 5,428,000 shares, including over-allotments, of common stock at
$29.50 per share. Net proceeds to the Company of $62.4 million were from
2,257,291 shares sold by the Company while 3,170,709 shares were sold by
certain stockholders. Costs of the offering, including underwriting
commissions, were $4.2 million.

Stock Plans

The Company has certain stock plans, which provide for the granting of up
to 4,515,833 nonqualified stock options, incentive stock options ("ISOs"),
stock appreciation rights and restricted stock awards to employees, directors
and consultants of the Company.

Under the terms of these stock plans, nonqualified options granted may not
be at a price of less than 50% of the fair market value of the common stock,
and ISOs granted may not be at a price of less than 100% of fair market value
of the common stock on the date of grant. All grants have been made at fair
market value under the plans. Options are generally exercisable commencing one
year after the date of grant at the rate of 20% per annum on a cumulative
basis. Nonqualified options expire up to ten years from the date of grant, and
ISOs expire five to ten years from the date of grant.

F-19
<PAGE>

ATMI, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(Continued)

10. Stockholders' Equity (continued)

<TABLE>
<CAPTION>
Number of Option Price
Shares Per Share
--------- -------------
<S> <C> <C>
Options outstanding at December 31, 1996........... 958,216 $ 0.28-$17.63
Granted.......................................... 1,023,506 $ 2.10-$40.13
Canceled......................................... (348,250) $ 0.53-$40.13
Exercised........................................ (82,520) $ 0.28-$13.50
--------- -------------
Options outstanding at December 31, 1997........... 1,550,952 $ 0.28-$29.38
Granted.......................................... 752,440 $14.00-$33.00
Canceled......................................... (110,130) $ 5.63-$33.00
Exercised........................................ (158,918) $ 0.28-$17.63
--------- -------------
Options outstanding at December 31, 1998........... 2,034,344 $ 0.28-$33.00
Granted.......................................... 1,148,954 $19.19-$37.38
Canceled......................................... (134,658) $ 5.63-$27.00
Exercised........................................ (204,085) $ 0.28-$29.38
--------- -------------
Options outstanding at December 31, 1999........... 2,844,555 $ 0.44-$37.38
========= =============
</TABLE>

At December 31, 1999 options for 1,017,946 shares were exercisable and
options for 805,667 shares were available for grant. Exercise prices for
282,340 options outstanding ranged from $0.44-$4.04; for 376,638 options
outstanding ranged from $5.63-$10.00; for 449,808 options outstanding ranged
from $10.13-$20.00; and for 956,820 options outstanding ranged from $20.88-
$24.25 and for 778,949 options ranged from $24.38-$37.38 as of December 31,
1999.

The weighted average exercise price and remaining contractual life of
options outstanding at December 31, 1999 was $18.94 and 7.8 years,
respectively.

As a result of the NOW and MST mergers in 1998 and 1999, respectively (see
Note 11), stock options of NOW and MST were converted into 205,089 and 123,016
of ATMI stock options. NOW stock options were converted into ATMI stock options
at historical prices ranging from $4.04 to $8.90 and MST stock options were
converted into ATMI stock options at historical prices ranging from $2.10 to
$15.74.

If compensation expense for the Company's plans had been determined for all
stock option grants based on the fair value at the grant dates for awards under
those plans, consistent with the method described in SFAS No. 123, the
Company's net income, net income per share-basic and net income per share-
assuming dilution would have been reduced to the pro forma amounts indicated
below (in thousands, except per share data):

<TABLE>
<CAPTION>
Pro forma
--------------------
1997 1998 1999
------ ------ ------
<S> <C> <C> <C>
Net income............................................. $5,556 $2,984 $6,948
Net income per share--basic............................ $ 0.24 $ 0.12 $ 0.26
Net income per share--assuming dilution................ $ 0.22 $ 0.11 $ 0.25
</TABLE>

F-20
<PAGE>

ATMI, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(Continued)

10. Stockholders' Equity (continued)

The fair value of each option grant, for pro forma disclosure purposes, was
estimated on the date of grant using the Black-Scholes option pricing model
with the following weighted average assumptions:

<TABLE>
<CAPTION>
1997 1998 1999
--------- --------- ---------
<S> <C> <C> <C>
Expected dividend yield........................ None None None
Risk free interest rate........................ 6.00% 5.50% 5.80%
Expected volatility............................ .560 .628 .615
Expected life of options....................... 7.5 years 7.5 years 7.5 years
</TABLE>

The weighted average fair value of non-canceled stock options granted in
1997, 1998 and 1999 was $17.04, $14.74 and $17.18, respectively.

Employee Stock Purchase Plan

The Employee Stock Purchase Plan ("ESPP Plan") was approved in May 1998 and
enables all employees to subscribe at six month intervals to purchase shares of
common stock at the lower of 85% of the fair market value of the shares on the
first day or last day of each six month period. A maximum of 500,000 shares is
authorized for subscription. At December 31, 1999, 64,000 shares have been
issued under the ESPP Plan, and no such shares were issued in 1998.

Earnings Per Share

The following table presents the computation of basic and diluted earnings
per share (in thousands, except per share data):

<TABLE>
<CAPTION>
1997 1998 1999
------ ------ -------
<S> <C> <C> <C>
Numerator:
Net income............................................. $6,395 $4,935 $10,546
====== ====== =======
Denominator:
Denominator for basic earnings per share--
Weighted-average shares............................... 23,617 25,645 26,440
Dilutive effect of contingent shares related to
acquisitions subject to escrow arrangements........... 1,289 1,289 1,149
Dilutive effect of employee stock options.............. 754 489 730
------ ------ -------
Denominator for diluted earnings per share............. 25,660 27,423 28,319
====== ====== =======
Net income per share--basic.............................. $ 0.27 $ 0.19 $ 0.40
====== ====== =======
Net income per share--assuming dilution.................. $ 0.25 $ 0.18 $ 0.37
====== ====== =======
</TABLE>

Options to purchase 16,000, 720,520 and 18,900 shares of common stock,
outstanding as of December 31, 1997, 1998 and 1999, respectively, were not
included in the computation of diluted earnings per share because their
exercise prices were greater than the average market price of the common shares
and, therefore, their inclusion would be antidilutive.

F-21
<PAGE>

ATMI, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(Continued)

11. Mergers and Acquisitions

The Company has consummated eight mergers since 1997 each of which has been
accounted for as a pooling of interests. The entities acquired and share
consideration exchanged were as follows:

<TABLE>
<CAPTION>
Shares Held in
Escrow
December 31,
Company Year Shares Issued 1999
------- ---- ------------- --------------
<S> <C> <C> <C>
ADCS Group (Note 8)......................... 1997 5,469,000 700,000
Lawrence Semiconductor Laboratories, Inc. .. 1997 3,671,000 --
NOW Technologies, Inc. ..................... 1998 1,594,000 --
TeloSense Corporation....................... 1999 232,000 --
Advanced Chemical Systems International,
Inc. ...................................... 1999 1,202,000 61,000
Delatech Incorporated....................... 1999 2,347,000 234,000
NewForm N.V. ............................... 1999 550,000 55,000
MST Analytics, Inc. ........................ 1999 993,000 99,000
</TABLE>

The former securityholders of the aforementioned entities have agreed to
indemnify the Company from and against certain losses arising out of breaches
of representations and warranties made by the respective securityholders. As
security for these obligations, the former securityholders agreed to escrow a
certain specified amount of the merger consideration. These shares will be
released from escrow in accordance with the terms of the respective merger
agreements.

The Company has reduced retained earnings by $102,000 and $163,000 in 1998
and 1999, respectively, to adjust retained earnings for the different fiscal
year ends of certain of the acquired entities.

In connection with the investigation, analysis and closings of the
aforementioned transactions, the Company recorded merger costs and related
expenses of $9.0 million, $1.7 million and $10.5 million in 1997, 1998, and
1999, respectively. During 1999, the Company reversed approximately $0.6
million of merger costs accrued in prior years. Included within merger costs
and related expenses in 1999 is a charge of $4.4 million related to the
Delatech acquisition to recognize the impaired value of certain inventory ($1
million) and goodwill ($3.4 million) associated with an existing environmental
equipment product line. These charges were based on the estimate of future cash
flows on a discounted basis compared with the carrying value of these assets.

For the years ended December 31, 1997 and 1998, prior to the acquisitions,
revenues and net income of acquired companies included in the financial
statements are as follows (in thousands):

<TABLE>
<CAPTION>
1997 1998
-------- -------
<S> <C> <C>
Revenues:
ATMI..................................................... $101,877 $97,874
TeloSense, ACSI and Delatech............................. $ 62,043 $42,994
NewForm and MST.......................................... $ 13,237 $24,238
NOW...................................................... $ 14,855 --
Net Income (Loss):
ATMI..................................................... $ 4,421 $ 6,465
TeloSense, ACSI and Delatech............................. $ 1,228 $(2,024)
NewForm and MST.......................................... $ (762) $ 494
NOW...................................................... $ 1,508 --
</TABLE>

F-22
<PAGE>

ATMI, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(Continued)

11. Mergers and Acquisitions (continued)

On July 15, 1997, MST acquired 100% of the outstanding capital stock of
four operating companies (i) Environmental Monitoring Technology S.A., a Swiss
holding company which owns 100% of the stock of MST Measurement Systems, Inc.;
(ii) Micro-Sensor Technologie GmbH; (iii) FPM Analytics, Inc. and (iv) Sensoric
GmbH ("four operating companies"). The aggregate purchase price for the four
operating companies was $18.8 million which was composed of cash of $5.6
million, the issuance of stock, and a two-year promissory note of $0.1 million.

The acquisition was accounted for as a purchase and, accordingly, the
operating results of the four operating companies have been included in the
Company's consolidated financial statements since the date of acquisition (July
15, 1997). The excess of the aggregate purchase price over the fair market
value of the net assets acquired of $4.4 million is being amortized over 10
years. The following unaudited pro forma consolidated results of operations for
the year ended December 31, 1997 assume that the acquisition of the four
operating companies occurred as of January 1, 1997 (in thousands, except per
share data):

<TABLE>
<CAPTION>
1997
--------
<S> <C>
Net revenues....................................................... $200,256
Income before taxes and minority interest.......................... $ 15,485
Net income......................................................... $ 6,893
Net income per share assuming dilution............................. $ 0.27
</TABLE>

12. Comprehensive Income

During 1998, the Company adopted FASB Statement No. 130, "Reporting
Comprehensive Income." Statement No. 130 requires the reporting of
comprehensive income in addition to net income from operations. Comprehensive
income is a more inclusive financial reporting methodology that includes
disclosure of certain financial information that historically has not been
recognized in the calculation of net income.

The components of comprehensive income are as follows (in thousands):

<TABLE>
<CAPTION>
Currency Unrealized Gain (Loss)
Translation on Available-for-Sale
Adjustments Securities Total
----------- ---------------------- -------
<S> <C> <C> <C>
Balance at December 31, 1996....... $ (78) $ -- $ (78)
Cumulative translation adjustment.. (1,376) -- (1,376)
------- ------ -------
Balance at December 31, 1997....... (1,454) -- (1,454)
------- ------ -------
Unrealized loss on available-for-
sale securities
(net of tax benefit of $281)...... -- (500) (500)
Cumulative translation adjustment.. 801 -- 801
------- ------ -------
Balance at December 31, 1998....... (653) (500) (1,153)
------- ------ -------
Unrealized gain on available-for-
sale securities
(net of tax provision of $4,141).. -- 7,860 7,860
Cumulative translation adjustment.. (181) -- (181)
------- ------ -------
Balance at December 31, 1999....... $ (834) $7,360 $ 6,526
------- ------ -------
</TABLE>

F-23
<PAGE>

ATMI, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(Continued)

13. Severance Charge

During the fourth quarter of 1999, the Company terminated the employment of
four executive officers within its Materials division and one executive officer
within its Technologies division and recorded a charge of $2.3 million,
reflected in selling, general, and administrative expenses in the Company's
1999 results of operations. As of December 31, 1999, there were no payments
charged against this liability. Payments for this liability will be made in
2000.

14. Commitments and Contingencies

On May 15, 1997, LSL settled patent infringement litigation with an
equipment manufacturer, related to equipment used by LSL that was purchased
from another manufacturer. Under the terms of the related settlement agreement,
LSL paid the manufacturer $2.0 million during 1997 and agreed to purchase
reactors from the manufacturer assuming LSL's business conditions justify such
purchases. LSL had purchased a reactor at an approximate fair market value of
$2.5 million during the year ended December 31, 1997.

In December 1998, a former office employee initiated a legal proceeding
against the Company alleging personal injuries to her minor child (then unborn)
allegedly resulting from her exposure to various chemicals while employed by
the Company. The plaintiffs have claimed damages of $25.0 million and
unspecified exemplary damages. The Company has denied the plaintiffs' legal
allegations and is vigorously defending this action. While the Company cannot
predict the outcome of this proceeding at this time, the Company believes it is
without merit.

In the normal course of business, the Company is involved in various
lawsuits and claims. Although the ultimate outcome of any of these legal
proceedings cannot be determined at this time, management, including internal
counsel, does not believe that the outcome of these proceedings, individually
or in the aggregate, will have a material adverse effect on the Company's
financial position or results of operations.

F-24
<PAGE>

ATMI, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(Continued)

15. Segment and Geographic Data

During 1998, the Company adopted FASB Statement No. 131 "Disclosure About
Segments of an Enterprise and Related Information". The Company has two
segments: ATMI Materials and ATMI Technologies. The reportable segments are
each managed separately because they manufacture and distribute distinct
products with different production processes. The Company evaluates performance
and allocate resources based on operating profit or loss, not including
interest and other income or expense and income taxes. Intercompany sales are
not material among segments or operating divisions. The general corporate
assets primarily include cash and marketable securities, goodwill and other
long-lived assets.

The following tables provide reported results for each of these segments
(in thousands):

<TABLE>
<CAPTION>
For the year ended December 31,
----------------------------------
1997 1998 1999
---------- ---------- ----------
<S> <C> <C> <C>
Revenues
ATMI Materials.......... $ 83,060 $ 71,279 $ 96,711
ATMI Technologies....... 108,952 93,827 99,525
---------- ---------- ----------
Consolidated revenues... $ 192,012 $ 165,106 $ 196,236
========== ========== ==========
<CAPTION>
1997 1998 1999
---------- ---------- ----------
<S> <C> <C> <C>
Operating Income (Loss)
ATMI Materials.......... $ 17,757 $ 11,373 $ 19,335
ATMI Technologies....... 6,765 (3,241) 5,267
Merger costs and related
expenses............... (9,000) (1,700) (9,914)
---------- ---------- ----------
Consolidated operating
income................. $ 15,522 $ 6,432 $ 14,688
========== ========== ==========
<CAPTION>
1997 1998 1999
---------- ---------- ----------
<S> <C> <C> <C>
Consolidated Net Income
Operating income from
reportable segments.... $ 15,522 $ 6,432 $ 14,688
Other profit or (loss).. (539) 2,915 3,578
Income tax provision.... (8,588) (4,412) (7,720)
---------- ---------- ----------
Consolidated net
income................. $ 6,395 $ 4,935 $ 10,546
========== ========== ==========
<CAPTION>
At December 31,
----------------------
1998 1999
---------- ----------
<S> <C> <C> <C>
Identifiable Assets
ATMI Materials.......... $ 45,166 $ 60,717
ATMI Technologies....... 73,321 78,747
General corporate
assets................. 90,165 93,192
---------- ----------
Total consolidated
assets................. $ 208,652 $ 232,656
========== ==========
</TABLE>

F-25
<PAGE>

ATMI, INC.

NOTES TO CONSOLIDATED FINANCIAL STATEMENTS--(Continued)

15. Segment and Geographic Data (continued)

The Company's geographic data for the years ended December 31, 1997, 1998
and 1999 are as follows:

<TABLE>
<CAPTION>
Europe and
United States Pacific Rim Other Eliminations Total
------------- ----------- ---------- ------------ --------
In Thousands
<S> <C> <C> <C> <C> <C>
December 31, 1997
Total revenues...... $136,453 $42,829 $14,572 $(1,842) $192,012
Long-lived assets... $ 54,473 $ 1,734 $ 498 $ -- $ 56,705
December 31, 1998
Total revenues...... $112,445 $34,451 $20,779 $(2,569) $165,106
Long-lived assets... $ 60,457 $ 1,373 $ 653 $ -- $ 62,483
December 31, 1999
Total revenues...... $119,716 $54,563 $23,586 $(1,629) $196,236
Long-lived assets... $ 56,224 $ 1,589 $ 638 $ -- $ 58,451
</TABLE>

Revenues are attributed to countries based on the location of the customer.
No one specific country within the Pacific Rim or Europe accounted for greater
than 10% of consolidated revenues in 1997, 1998 and 1999. Revenues and net
income of the foreign subsidiaries is not material to the consolidated
operations of the Company for each of the three years in the period ended
December 31, 1999. The Company utilized one vendor to manufacture and
distribute product that accounted for approximately 7%, 10% and 14% of revenues
in 1997, 1998 and 1999, respectively.

F-26
<PAGE>

QUARTERLY RESULTS OF OPERATIONS (UNAUDITED)

(In thousands, except per share amounts)

<TABLE>
<CAPTION>
Quarter Year
--------------------------------------- --------
1998 First Second Third Fourth 1998
- ---- ------- ------- ------- ------- --------
<S> <C> <C> <C> <C> <C>
Revenues.................. $52,047 $44,446 $35,161 $33,452 $165,106
Gross profit.............. $28,528 $21,294 $14,907 $16,958 $ 81,687
Net income (loss)......... $ 5,747 $ 1,496 $(2,348)(a) $ 40 $ 4,935
Net income (loss) per
share--basic............. $ 0.24 $ 0.07 $ (0.09)(a) $ 0.00 $ 0.19
Net income (loss) per
share--assuming
dilution................. $ 0.22 $0.05 $ (0.09)(a) $ 0.00 $ 0.18
<CAPTION>
Quarter Year
--------------------------------------- --------
1999 First Second Third Fourth 1999
- ---- ------- ------- ------- ------- --------
<S> <C> <C> <C> <C> <C>
Revenues.................. $37,240 $49,323 $52,055 $57,618 $196,236
Gross profit.............. $18,999 $26,563 $26,973 $30,731 $103,266
Net income (loss)......... $ 1,479 $ (819)(b) $ 6,132 $ 3,754(c) $ 10,546
Net income (loss) per
share--basic............. $ 0.06 $ (0.03) $ 0.23 $ 0.14 $ 0.40
Net income (loss) per
share--assuming
dilution................. $ 0.05 $(0.03) $ 0.22 $ 0.13 $ 0.37
</TABLE>
- --------
(a) Includes merger costs and related expenses of $1.7 million incurred in
completing the NOW acquisition, and a severance charge of $0.4 million for
severance for employees. The severance was completed by December 31, 1998.
(b) Includes merger costs and related expenses of $7.2 million incurred in the
ACSI, Delatech, and TeloSense acquisitions.

(c) Includes merger costs and related expenses of $3.3 million incurred in
completing the MST Analytics and NewForm N.V. acquisitions, and a severance
charge of $2.3 million of severance for five executive officers of the
Materials and Technologies segments.

F-27
<PAGE>

SCHEDULE II

ATMI, INC.

VALUATION AND QUALIFYING ACCOUNTS

(In thousands)

<TABLE>
<CAPTION>
Balance at Balance at
Beginning Charged to End
Year Ended of Period Cost/Expense Deductions of Period
- ---------- ---------- ------------ ---------- ----------
<S> <C> <C> <C> <C>
December 31, 1997
Allowance for doubtful
accounts...................... $ 682 $1,251 $ 446(a) $1,487
Obsolescence reserve........... 952 1,608 823(b) 1,737
December 31, 1998
Allowance for doubtful
accounts...................... $1,487 $ 399 $ 927(a) $ 959
Obsolescence reserve........... 1,737 1,365 1,241(b) 1,861
Severance accrual.............. 0 402 402(c) 0
December 31, 1999
Allowance for doubtful
accounts...................... $ 959 $ 587 $ 180(a) $1,366
Obsolescence reserve........... 1,861 1,143 1,475(b) 1,529
Severance accrual.............. 0 2,300 0 2,300
</TABLE>
- --------

(a)Reflects write-offs of bad debts

(b)Reflects disposals of obsolete inventory

(c)Reflects payments made during 1998

F-28
<PAGE>

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

No dealer, salesperson or other person is authorized to give any information
or to represent anything not contained in this prospectus. You must not rely
on any unauthorized information or representations. This prospectus is an
offer to sell only the shares offered hereby, but only under circumstances and
in jurisdictions where it is lawful to do so. The information contained in
this prospectus is current only as of its date.

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

TABLE OF CONTENTS

<TABLE>
<CAPTION>
Page
----
<S> <C>
Prospectus Summary....................................................... 3
Risk Factors............................................................. 6
Special Note Regarding Forward-Looking Information....................... 11
Use of Proceeds.......................................................... 12
Dividend Policy.......................................................... 12
Price Range of Common Stock.............................................. 12
Capitalization........................................................... 13
Selected Consolidated Financial Data..................................... 14
Management's Discussion and Analysis of Financial Condition and Results
of Operations........................................................... 16
Business................................................................. 25
Management............................................................... 40
Selling Stockholders..................................................... 42
Description of Capital Stock............................................. 43
Underwriting............................................................. 46
Where Can You Find More Information...................................... 47
Legal Matters............................................................ 48
Experts.................................................................. 48
Index to Consolidated Financial Statements............................... F-1
</TABLE>

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

3,100,000 Shares

ATMI, Inc.

Common Stock

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

[LOGO]

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

Goldman, Sachs & Co.

Banc of America Securities LLC

Deutsche Banc Alex. Brown

Prudential Volpe Technology
a unit of Prudential Securities

Representatives of the Underwriters

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

PART II

INFORMATION NOT REQUIRED IN PROSPECTUS

Item 14. Other Expenses of Issuance and Distribution

The following table sets forth the estimated expenses, other than
underwriting discounts and commissions, payable by the registrant in connection
with the sale and distribution of the shares of Common Stock registered hereby.
The registrant is paying all of the expenses incurred on behalf of the selling
stockholders (other than discounts and commissions).

<TABLE>
<S> <C>
SEC registration fee.................................................. $ 45,587
NASD filing fees...................................................... 17,545
Nasdaq National Market listing fee.................................... 17,500
Printing expenses..................................................... 175,000
Legal fees and expenses............................................... 150,000
Accounting fees and expenses.......................................... 175,000
Transfer agent and registrar fees and expenses........................ 1,500
Miscellaneous......................................................... 17,868
--------
Total expenses...................................................... $600,000
========
</TABLE>

Item 15. Indemnification of Directors and Officers

The registrant's Certificate of Incorporation provides that the personal
liability of the directors of the registrant shall be limited to the fullest
extent permitted by the provisions of Section 102(b)(7) of the General
Corporation Law of the State of Delaware (the "DGCL"). Section 102(b)(7) of the
DGCL generally provides that no director shall be liable personally to the
registrant or its stockholders for monetary damages for breach of fiduciary
duty as a director; however, the Certificate of Incorporation does not
eliminate the liability of a director for (i) any breach of the director's duty
of loyalty to the registrant or its stockholders; (ii) acts or omissions not in
good faith or that involve intentional misconduct or a knowing violation of
law; (iii) acts or omissions in respect of certain unlawful dividend payments
or stock redemptions or repurchases; or (iv) any transaction from which such
director derives improper personal benefit. The effect of this provision is to
eliminate the rights of the registrant and its stockholders (through
stockholders' derivatives suits on behalf of the registrant) to recover
monetary damages against a director for breach of her or his fiduciary duty of
care as a director (including breaches resulting from negligent or grossly
negligent behavior) except in the situations described in clauses (i) through
(iv) above. The limitations summarized above, however, do not affect the
ability of the registrant or its stockholders to seek nonmonetary remedies,
such as an injunction or rescission, against a director for breach of her or
his fiduciary duty.

In addition, the registrant's Certificate of Incorporation and Bylaws
provide that the registrant shall, to the fullest extent permitted by Section
145 of the DGCL, indemnify all persons whom it may indemnify pursuant to
Section 145 of the DGCL. Section 145 of the DGCL permits a company to indemnify
an officer or director who was or is a party or is threatened to be made a
party to any proceeding because of his or her position, if the officer or
director acted in good faith and in a manner he or she reasonably believed to
be in or not opposed to the best interests of the company and, with respect to
any criminal action or proceeding, had no reasonable cause to believe his or
her conduct was unlawful. Insofar as indemnification for liabilities arising
under the Securities Act of 1933, as amended (the "Securities Act"), may be
permitted to directors, officers, or persons controlling the registrant
pursuant to the foregoing provisions, the registrant has been informed that in
the opinion of the Securities and Exchange Commission (the "Commission"), such
indemnification is against public policy as expressed in the Securities Act and
is therefore unenforceable.

II-1
<PAGE>

The registrant maintains insurance for officers and directors against
certain liabilities, including liabilities under the Securities Act. The effect
of this insurance is to indemnify any officer or director of the registrant
against expenses, including, without limitation, attorneys' fees, judgments,
fines and amounts paid in settlement, incurred by an officer or director upon a
determination that such person acted in good faith. The premiums for such
insurance are paid by the registrant.

Item 16. Exhibits

The following is a list of exhibits filed as a part of this registration
statement or incorporated by reference herein:

<TABLE>
<CAPTION>
Exhibit
No. Description
------- -----------
<C> <S>
1.1 Form Underwriting Agreement. (1)
4.1(a) Certificate of Incorporation of ATMI (Exhibit 3.01 to ATMI's
Registration Statement on Form S-4, filed September 10, 1997,
Registration No. 333-35323 (the "1997 Form S-4 Registration
Statement")). (2)
4.1(b) Certificate of Amendment to Certificate of Incorporation (Exhibit
4.1(b) to ATMI's Post-Effective Amendment No. 1 to Registration
Statement on Form S-8, filed October 10, 1997, Registration No. 33-
77060). (2)
4.1(c) Certificate of Amendment to Certificate of Incorporation (Exhibit
3.01(c) to ATMI's Registration Statement on Form S-4, Registration No.
333-51333). (2)
4.2 Bylaws of ATMI (Exhibit 3.02 to the 1997 Form S-4 Registration
Statement). (2)
5.1 Opinion and Consent of Shipman & Goodwin LLP as to the legality of the
shares to be registered. (1)
23.1 Consent of Shipman & Goodwin LLP (to be included in the opinion filed
as Exhibit 5.1). (1)
23.2 Consent of Ernst & Young LLP. (3)
23.3 Consent of Deloitte & Touche LLP. (3)
23.4 Consent of Arthur Andersen LLP. (3)
23.5 Consent of Rath, Anders, Dr. Wanner & Partner. (3)
24.1 Power of Attorney, included in signature page of this Registration
Statement. (1)
</TABLE>
- --------

(1)Previously filed.
(2)Incorporated by reference.

(3)Filed herewith.

Item 17. Undertakings

The undersigned registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act, each filing of the
registrant's annual report pursuant to Section 13(a) or Section 15(d) of the
Securities Exchange Act of 1934 (and, where applicable, each filing of an
employee benefit plan's annual report pursuant to Section 15(d) of the
Securities Exchange Act of 1934) that is incorporated by reference in the
Registration Statement shall be deemed to be a new registration statement
relating to the securities offered therein, and the offering of such securities
at that time shall be deemed to be the initial bona fide offering thereof.

Insofar as indemnification for liabilities arising under the Securities Act
may be permitted to the directors, officers and controlling persons of the
registrant pursuant to the foregoing provisions, or otherwise, the registrant
has been advised that in the opinion of the Commission such indemnification is
against public policy as expressed in the Securities Act and is, therefore,
unenforceable. In the event that a claim for indemnification against such
liabilities (other than the payment by the registrant of expenses incurred or
paid by a director, officer or controlling person of the registrant in the
successful defense of any action, suit or proceeding) is asserted by such
director, officer or controlling person in connection with the securities being
registered, the registrant

II-2
<PAGE>

will, unless in the opinion of its counsel the matter has been settled by
controlling precedent, submit to a court of appropriate jurisdiction the
question whether such indemnification by it is against public policy as
expressed in the Securities Act and will be governed by the final adjudication
of such issue.

The undersigned registrant hereby undertakes that:

(1) For purposes of determining any liability under the Securities
Act, the information omitted from the form of prospectus filed as part of
this registration statement in reliance upon Rule 430A and contained in a
form of prospects filed by the registrant pursuant to Rule 424(b)(1) or
(4) or 497(h) under the Securities Act shall be deemed to be part of this
registration statement as of the time it was declared effective.

(2) For the purpose of determining any liability under the Securities
Act, each post-effective amendment that contains a form of prospectus
shall be deemed to be a new registration statement relating to the
securities offered therein, and the offering of such securities at that
time shall be deemed to be the initial bona fide offering thereof.

II-3
<PAGE>

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the registrant
certifies that it has reasonable grounds to believe that it meets all of the
requirements for filing on Form S-3 and has duly caused this registration
statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Danbury, State of Connecticut, on March 16, 2000.

ATMI, INC.

/s/ Eugene G. Banucci
By: _________________________________
Eugene G. Banucci, President,
Chief Executive Officer and
Chairman of the Board

Pursuant to the requirements of the Securities Act of 1933, this
registration statement has been signed by the following persons in the
capacities and on the dates indicated.

<TABLE>
<CAPTION>
Signature Title Date
--------- ----- ----

<S> <C> <C>
/s/ Eugene G. Banucci President, Chief Executive March 16, 2000
______________________________________ Officer and Chairman of
Eugene G. Banucci the Board (principal
executive officer)

/s/ Daniel P. Sharkey Vice President, Treasurer March 16, 2000
______________________________________ and Chief Financial
Daniel P. Sharkey Officer (principal
financial and accounting
officer)

/s/ Mark A. Adley* Director March 16, 2000
______________________________________
Mark A. Adley

/s/ Robert S. Hillas* Director March 16, 2000
______________________________________
Robert S. Hillas

/s/ Kam Law* Director March 16, 2000
______________________________________
Kam Law

/s/ Stephen H. Mahle* Director March 16, 2000
______________________________________
Stephen H. Mahle

/s/ Stephen H. Siegele* Director March 16, 2000
______________________________________
Stephen H. Siegele

/s/ Daniel P. Sharkey
*By:__________________________________
Daniel P. Sharkey
Attorney-in-fact
</TABLE>

II-4
<PAGE>

EXHIBIT INDEX

<TABLE>
<CAPTION>
Exhibit No. Description
----------- -----------
<C> <S>
1.1 Form Underwriting Agreement. (1)
4.1(a) Certificate of Incorporation of Registrant (Exhibit 3.01 to ATMI's
Registration Statement on Form S-4, filed September 10, 1997,
Registration No. 333-35323 (the "1997 Form S-4 Registration
Statement")). (2)
4.1(b) Certificate of Amendment to Certificate of Incorporation (Exhibit
4.1(b) to ATMI's Post-Effective Amendment No. 1 to Registration
Statement on Form S-8, filed October 10, 1997, Registration No.
33-77060). (2)
4.1(c) Certificate of Amendment to Certificate of Incorporation (Exhibit
3.01(c) to ATMI's Registration Statement on Form S-4, Registration
No. 333-51333). (2)
4.2 Bylaws of ATMI (Exhibit 3.02 to the 1997 Form S-4 Registration
Statement). (2)
5.1 Opinion and Consent of Shipman & Goodwin LLP as to the legality of
the shares to be registered. (1)
23.1 Consent of Shipman & Goodwin LLP (to be included in the opinion
filed as Exhibit 5.1). (1)
23.2 Consent of Ernst & Young LLP. (3)
23.3 Consent of Deloitte & Touche LLP. (3)
23.4 Consent of Arthur Andersen LLP. (3)
23.5 Consent of Rath, Anders, Dr. Wanner & Partner. (3)
24.1 Power of Attorney, included in signature page of this Registration
Statement. (1)
</TABLE>
- --------

(1)Previously filed.
(2)Incorporated by reference.

(3)Filed herewith.

<PAGE>

Exhibit 23.2

CONSENT OF INDEPENDENT AUDITORS

We consent to the reference to our firm under the caption "Experts" and to the
use of our report dated February 7, 2000 in Amendment No. 1 to the Registration
Statement (Form S-3 No. 333-31982) and related Prospectus of ATMI, Inc. for the
registration of 3,565,000 shares of its common stock.

We also consent to the incorporation by reference therein of our report dated
February 7, 2000, with respect to the consolidated financial statements and
schedule of ATMI included in its Annual Report (Form 10-K) for the year ended
December 31, 1999, filed with the Securities and Exchange Commission.

/s/ Ernst & Young LLP

Stamford, Connecticut

March 16, 2000

<PAGE>

Exhibit 23.3

INDEPENDENT AUDITORS' CONSENT

We consent to the use and incorporation by reference in this Registration
Statement of ATMI, Inc. on Form S-3 of our report dated May 1, 1998 relating to
the consolidated financial statements of NOW Technologies, Inc. and
Subsidiaries for the year ended March 31, 1998 appearing in ATMI, Inc.'s Annual
Report on Form 10-K for the year ended December 31, 1999. We also consent to
the reference to us under the heading "Experts" in such Registration Statement.

/s/ Deloitte & Touche LLP

Minneapolis, Minnesota

March 16, 2000

<PAGE>

Exhibit 23.4

Consent of Independent Accountants

As independent public accountants, we hereby consent to the use and
incorporation by reference in this registration statement of our report dated
May 28, 1999 included in ATMI, Inc.'s Form 10-K for the year ended December 31,
1999 and all references to our Firm included in this registration statement. We
also consent to the application of our reports to the schedule included in that
10-K labeled "Valuation and Qualifying Accounts" as of the date and period
covered by our report.

/s/ Arthur Andersen LLP

Chicago, Illinois

March 16, 2000

<PAGE>

Exhibit 23.5

CONSENT OF INDEPENDENT AUDITORS

As independent public accountants, we hereby consent to the use and
incorporation by reference in this registration statement of our reports dated
January 22, 1999 included in ATMI, Inc.'s Form 10-K for the year ended December
31, 1999 and all references to our Firm included in this registration
statement. We also consent to the application of our reports to the schedule
labeled "Valuation and Qualifying Accounts" as of the dates and period covered
by our reports.

Rath, Anders, Dr. Wanner & Partner

Munich, March 16, 2000

/s/ Kabisch
Dipl.--Kfm. Kabisch
Vereidigter Buchprufer

/s/ Metzler
Dipl.--Kfm. Metzler
Wirtschaftsprufer