<PAGE>

   As filed with the Securities and Exchange Commission on October 25, 1999

                                                   Registration No. 333-
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
                      SECURITIES AND EXCHANGE COMMISSION

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

                                ---------------
                     APPLIED SCIENCE AND TECHNOLOGY, INC.
            (Exact name of registrant as specified in its charter)

              DELAWARE                              04-2962110
   (State or other jurisdiction of      (I.R.S. Employer Identification No.)
   incorporation or organization)

                                ---------------
                   RICHARD S. POST, CHIEF EXECUTIVE OFFICER
                     APPLIED SCIENCE AND TECHNOLOGY, INC.
                                 35 CABOT ROAD
                          WOBURN, MASSACHUSETTS 01801
                                (781) 933-5560
     (Address, including zip code, and telephone, including area code, of
                   registrant's principal executive offices)

                                ---------------
                                   Copy to:
                           NEIL H. ARONSON, ESQUIRE
              MINTZ, LEVIN, COHN, FERRIS, GLOVSKY AND POPEO, P.C.
                             ONE FINANCIAL CENTER
                          BOSTON, MASSACHUSETTS 02111
                                (617) 542-6000

                                ---------------
   Approximate date of commencement of proposed sale to the public: From time
to time after this Registration Statement becomes effective.
   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, check the following box. [X]
   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. [_]

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

                        CALCULATION OF REGISTRATION FEE

-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
<TABLE>
<CAPTION>
Title of each class
        of           Amount to  Proposed maximum Proposed maximum  Amount of
 securities to be        be      offering price     aggregate     registration
    registered       registered    per share      offering price      fee
------------------------------------------------------------------------------
<S>                  <C>        <C>              <C>              <C>
Common Stock, $.01
 par value per
 share.............   325,873       $23.88(1)      $7,780,218(1)  $2,162.90(1)
------------------------------------------------------------------------------
Total Registration
 Fee...............                                               $2,162.90(1)
</TABLE>
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
(1) Estimated solely for the purpose of calculating the amount of the
    registration fee. Pursuant to Rule 457(c) of the Securities Act of 1933,
    the proposed maximum offering price has been calculated based upon the
    average of the high and low sale prices of our common stock as reported by
    the NASDAQ National Market System on October 19, 1999.

   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 the registration statement
shall become effective on such date as the commission, acting pursuant to said
section 8(a), shall determine.
-------------------------------------------------------------------------------
-------------------------------------------------------------------------------
<PAGE>

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
+The information in this prospectus is not complete and may be changed. We may +
+not sell these securities until the registration statement filed with the     +
+Securities and Exchange Commission is effective. This prospectus is not an    +
+offer to sell these securities and is not soliciting an offer to buy these    +
+securities in any state where the offer or sale is not permitted.             +
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
                                   PROSPECTUS

                     Subject to Completion, Dated

                      APPLIED SCIENCE AND TECHNOLOGY, INC.

                         325,873 Shares of Common Stock


 . We are registering a
  total of 325,873 shares
  of our common stock for
  sale by the
  securityholders
  identified in this
  prospectus as the
  selling stockholders.


 . The selling                       This Investment
  stockholders may sell                Involves
  the common stock at              A High Degree of
  prices and on terms              Risk. You Should
  determined by the                    Purchase
  market, in negotiated             Shares Only If
  transactions or through           You Can Afford
  underwriters. The                A Complete Loss.
  selling stockholders
  may also sell the
  common stock under Rule
  144 of the Securities
  Act of 1933. The
  selling stockholders
  are identified and
  information with
  respect to them is
  provided under the
  caption "Selling
  Stockholders" in this
  prospectus.


 . We will not receive any
  of the proceeds from
  the sale of the common
  stock being registered.


 . Our common stock trades
  on the NASDAQ National
  Market System under the
  symbol "ASTX."


  On October 21, 1999, the closing sale price of one share of our common stock
           as quoted on the NASDAQ National Market System was $25.50.

Neither the Securities and Exchange Commission nor any state securities
commission has approved or disapproved of these securities or determined if
this prospectus is truthful or complete. It is illegal for any person to tell
you otherwise.

The information in this prospectus is not complete and may be changed. A
registration statement relating to these securities has been filed with the
Securities and Exchange commission. No one may sell these securities nor may
offers to buy be accepted until the registration statement filed with the
Securities and Exchange Commission is effective. This prospectus is not an
offer to sell these securities and is not soliciting an offer to buy these
securities in any state where the offer, solicitation or sale is not permitted.

                The date of this Prospectus is October 25, 1999

<PAGE>

                      WHERE YOU CAN FIND MORE INFORMATION

   We are a public company and file annual, quarterly and special reports,
proxy statements and other information with the Securities and Exchange
Commission. You may read and copy any document we file at the SEC's Public
Reference Room at 450 Fifth Street, N.W., Washington, D.C. 20549. You can
request copies of these documents by writing to the SEC and paying a fee for
the copying cost. Please call the SEC at 1-800-SEC-0330 for more information
about the operation of the public reference room. Our SEC filings are also
available to the public at the SEC's web site at "http://www.sec.gov." In
addition, our stock is listed for trading on the NASDAQ National Market. You
can read and copy reports and other information concerning us at the offices of
NASDAQ Operations at 1735 K Street, N.W., Washington, D.C. 20006.

   This prospectus is only part of a Registration Statement on Form S-3 that we
have filed with the SEC under the Securities Act of 1933 and therefore omits
certain information contained in the Registration Statement. We have also filed
exhibits and schedules with the Registration Statement that are excluded from
this prospectus, and you should refer to the applicable exhibit or schedule for
a complete description of any statement referring to any contract or other
document. You may:

  . inspect a copy of the Registration Statement, including the exhibits and
    schedules, without charge at the public reference room or

  . obtain a copy from the SEC upon payment of the fees prescribed by the
    SEC.

                    INCORPORATION OF DOCUMENTS BY REFERENCE

   The SEC allows us to "incorporate by reference" the information we file with
it, 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 a part of this prospectus and information that we file later with the SEC
will automatically update and supersede this information. We incorporate by
reference the documents listed below and any future filings made with the SEC
under Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934
until all of the shares of common stock are sold. The documents we are
incorporating by reference are:

  . Our Annual Report on Form 10-K for the fiscal year ended June 26, 1999,
    filed on September 24, 1999 (File No. 1-09898);

  . Our Proxy Statement, filed on October 20, 1999; and

  . The description of our capital stock contained in our registration
    statement on Form 8-A under the 1934 Act (File No. 0-22646), including
    amendments or reports filed for the purpose of updating that description.

   You may request a copy of these filings at no cost by writing or telephoning
our Director of Investor and Public Relations at the following address and
phone number:

    Applied Science and Technology, Inc.
    35 Cabot Road
    Woburn, Massachusetts 01801
    (781) 933-5560

   This prospectus is part of a Registration Statement that we filed with the
SEC. You should rely only on the information incorporated by reference in or
provided in this prospectus and the Registration Statement. We have not
authorized any other person to provide you with different information. We are
not making an offer of these securities in any state where the offer is not
permitted. You should not assume that the information in this prospectus is
accurate as of any date other than the date on the front of this document.

                                       2
<PAGE>

                               PROSPECTUS SUMMARY

   This summary highlights information incorporated by reference or contained
elsewhere in this prospectus. It is not complete and may not contain all of the
information that you should consider before investing in our securities. You
should read the entire prospectus and the documents incorporated by reference
herein carefully, including the "Risk Factors" section contained in our most
recent report on Form 10-K for the fiscal year ended June 26, 1999, and you
must consult the more detailed financial statements, and notes to financial
statements, incorporated by reference in this prospectus.

   This prospectus and the documents incorporated by reference contain forward-
looking statements. These statements can be identified by the use of forward-
looking terminology such as "may," "will," "could," "expect," "anticipate,"
"estimate," "continue" or other similar words. These statements discuss future
expectations, contain projections of results of operations or of financial
condition or state other forward-looking information. Examples of forward-
looking statements can be found in the discussion set forth under "Management's
Discussion and Analysis of Financial Condition and Results of Operations" in
our Annual Report on Form 10-K for the fiscal year ended June 26, 1999 and
under "Business" in the Form 10-K, incorporated in this prospectus by
reference. Such statements are based on current expectations that involve a
number of uncertainties including those set forth in the risk factors below.
When considering forward-looking statements, you should keep in mind that the
risk factors incorporated by reference could cause our actual results to differ
significantly from those contained in any forward-looking statement.

                                  The Company

   We supply precision reactive gas processing solutions and specialty power
sources to the semiconductor, electronics, medical and industrial markets. Our
broad product line is based on one or more of our core technologies including
reactive gas processing, power sources and system integration. Depending on our
customers' needs, we provide varying levels of integration--from components to
integrated subsystems to complete process systems. Our reactive gas solutions
give our customers a competitive advantage by improving their time to market
with lower costs and less complexity.

   The electronics revolution could not have taken place without the advent of
reactive gas processing methods for production of semiconductors. A reactive
gas, created when energy breaks apart the molecules in a stable gas, allows
rapid chemical reactions to occur at relatively low temperatures, essential for
manufacturing advanced electronic devices. The semiconductor industry is the
largest user of precision reactive gas processing because of its extraordinary
demands for ultra-pure, high-yield and fine-geometry processes.

   We sell an extensive line of integrated subsystems and components to leading
semiconductor equipment manufacturers, such as Applied Materials, which
incorporate our products into the equipment it sells to semiconductor
manufacturers. Semiconductor technology advances, particularly shrinking line
widths, are driving the need for more sophisticated manufacturing processes
which increasingly involve the use of reactive gases. Many essential steps in
the manufacture of semiconductors use reactive gas processes including
photoresist stripping, etching, thin-film deposition, surface and chamber
cleaning and abatement of toxic exhaust gases. As equipment companies seek to
improve the efficiency of their development and manufacturing processes, they
are working more closely with critical suppliers who can provide integrated
subsystems. We deliver fully-integrated reactive gas solutions that address
this opportunity.

   Precision reactive gas technologies are increasingly being used in other
sectors of electronics including magnetic disk heads and advanced electronics
packaging. For these applications, we sell complete process systems which
incorporate our reactive gas solutions combined with a fully-integrated
platform that includes substrate handling and a production process.

   We sell power source and reactive gas products for medical equipment and a
variety of industrial applications. Our power sources are used in magnetic
resonance imaging (MRI), medical lasers and medical

                                       3
<PAGE>

apparatus sterilization. Industrial applications include power sources for
laser markers and high intensity lamps and reactive gas sources for thin-film
optical coating, polymer surface modification and removal of trace carcinogens
from groundwater.

   Our principal executive offices are located at 35 Cabot Road, Woburn,
Massachusetts 01801-1053 and our telephone number is (781) 933-5560. Our
corporate web site is www.astex.com.

                                       4
<PAGE>

                                USE OF PROCEEDS

   We will not receive any of the proceeds from the sale of the common stock
by the selling stockholders.

                           DESCRIPTION OF SECURITIES

Authorized and Outstanding Capital Stock

   Pursuant to our Certificate of Incorporation, as amended, we are authorized
to issue up to 30,000,000 shares of our common stock, $.01 par value per share
and 1,000,000 shares of preferred stock. At June 26, 1999, we had issued
11,417,162 shares of common stock and no shares of preferred stock. As of
June 26, 1999, we had also issued options to purchase up to 1,370,333 shares
of common stock to employees, directors and others pursuant to our stock
option plans, at an average exercise price of $7.65 per share.

Common Stock

   The holders of Common Stock are entitled to one vote per share for each
share held of record on all matters submitted to a vote of stockholders and
are entitled to receive ratably such dividends as may be declared by the Board
of Directors out of funds legally available therefor. In the event of a
liquidation, dissolution or winding up of the Company, holders of Common Stock
have the right to a ratable portion of assets remaining after payment of
liabilities and the liquidation preferences of any outstanding Preferred
Stock. The holders of Common Stock have no preemptive rights or rights to
convert their Common Stock into any other securities and are not subject to
future calls or assessments by the Company. All outstanding shares of Common
Stock are fully paid and non-assessable.

Preferred Stock and Preferred Share Purchase Rights

   The Board of Directors may, without further action of our stockholders,
issue preferred stock in one or more series and fix the rights and preferences
thereof, including dividend rights, dividend rates, conversion rights, voting
rights, terms of redemption (including sinking fund provisions), redemption
price or prices, liquidation preferences and the number of shares constituting
any series or the designation of such series.

   On February 19, 1998, we declared a dividend of one preferred share
purchase right (a "right") for each outstanding share of common stock
outstanding on March 2, 1998 (the "record date") to stockholders of record on
that date. Each right entitles the registered holder to purchase one one-
thousandth of a share of Series A Junior Participating Preferred Stock, par
value $0.01 per share ("junior preferred shares") at $70 per one one-
thousandth of a junior preferred share, subject to adjustment in the event of
a stock split of the common shares or a stock dividend on the common shares
payable in common shares or subdivisions, consolidations or combinations of
the common shares occurring prior to the distribution date, defined below.

   Until the earlier of (i) 10 days following a public announcement that a
person or group of affiliated or associated persons has acquired a beneficial
ownership of 15% or more of the outstanding common shares or (ii) 10 business
days following the commencement of, or announcement of an intention to make, a
tender offer or exchange offer the consummation of which would result in the
beneficial ownership by a person or group of 15% or more of such outstanding
common shares (the earlier of such dates being the "distribution date"), the
rights will be evidenced, with respect to any of the common share certificates
outstanding as of the record date.

   Until the distribution date, the rights will be transferred with and only
with the common shares. Until the distribution date (or earlier redemption or
expiration of the rights), new common share certificates issued after the
record date will contain a notation incorporating the rights agreement by
reference.

   Preferred shares purchased upon exercise of the rights are not redeemable
and are entitled to quarterly dividend payments of 1000 times dividends
declared on common shares, 1000 votes, voting together with common shares, and
1000 times the aggregate payment made to common shareholders in the event of
liquidation.

                                       5
<PAGE>

   The rights are not exercisable until the distribution date and expire on
December 31, 2007, unless extended or redeemed by us.

   The future issuance of preferred stock could reduce the rights, including
voting rights, of the holders of common stock, and, therefore, reduce the
value of the common stock. In particular, specific rights granted to future
holders of preferred stock could be used to restrict our ability to merge with
or sell our assets to a third party, thereby preserving our control by
existing management.

                         TRANSFER AGENT AND REGISTRAR

   The transfer agent and registrar for our common stock is Continental Stock
Transfer and Trust Company.

                                       6
<PAGE>

                              SELLING STOCKHOLDERS

   The following table lists the selling stockholders and provides information
regarding the beneficial ownership of our common stock by each selling
stockholder as of October 14, 1999 (unless otherwise noted). The information
provided in the table has been obtained from the selling stockholders. The
selling stockholders may sell all, some or none of their securities in this
offering. See "Plan of Distribution" on page 6 of this prospectus.

<TABLE>
<CAPTION>
                                                              Percentage of
                                                                 Shares
                                               Maximum Number Beneficially
                           Number of Shares      of Shares     Owned (/1/)
     Names of Selling        Beneficially          Being      -----------------
       Stockholders           Owned(/1/)        Offered(/1/)         Percent
     ----------------      ----------------    -------------- ------ ----------
<S>                        <C>                 <C>            <C>    <C>
Chunghsin Lee.............          142,792           142,792             1.2%
Piero Sferlazzo...........           46,274(2)         40,274               *
David Felsenthal..........           21,842(3)         16,842               *
Chen-Chun Lin.............           12,204            12,204               *
Lydia Chang Lee...........           12,204            12,204               *
William Holber, Ph.D. ....           45,965(4)          9,279               *
Jung-Fa Lee...............            9,763             9,763               *
Jerald M. Blaze...........            7,322             7,322               *
Jeng-Li Wu................            7,322             7,322               *
Shu Yen Lin...............            6,102             6,102               *
Wen-Chang Wang............            6,102             6,102               *
Ming-Liang Hu.............            6,102             6,102               *
Huei-Huanz Chen...........            3,661             3,661               *
Hui-Yeng Chen.............            3,661             3,661               *
Jen-Yi Hung...............            3,661             3,661               *
Ming-Chui Lee.............            3,661             3,661               *
Yu-Mei Hsieh..............            3,661             3,661               *
Ching-Lian Hsieh..........            3,661             3,661               *
Hung-Yen Chuang...........            3,661             3,661               *
Hsiang-Chia Cheng.........            3,661             3,661               *
Tien-Chun Chen............            3,661             3,661               *
Chune-Dar Hwang...........            3,051             3,051               *
Michael Silvia............           17,879             3,000               *
Matthew Besen.............           24,400             3,000               *
Rosemary Hewett...........            3,129             2,929               *
Vickie J. Risteen.........            2,296             2,196               *
Chiao-Chuan Chen..........            1,220             1,220               *
Tsan-Ying Wang............            1,220             1,220               *
  Total...................                            325,873             2.8%
</TABLE>
--------
*   Less than one percent of the outstanding shares of common stock.

(1) Percentage ownership is based upon 11,479,630 shares of common stock issued
    and outstanding as of October 14, 1999. Beneficial ownership of common
    stock is determined in accordance with the rules of the SEC and generally
    includes voting or investment power with respect to securities. Shares of
    common stock subject to options, warrants and convertible securities
    currently exercisable or convertible, or exercisable or convertible within
    60 days of October 14, 1999 are considered to be outstanding for purposes
    of computing the percentage ownership of the persons holding such option,
    warrant or convertible security, but not for purposes of computing the
    percentage of any other holder. Unless otherwise noted, beneficial
    ownership is as of October 14, 1999.

(2) Includes 6,000 shares of common stock subject to currently exercisable
    options held by Dr. Sferlazzo.

(3) Includes 5,000 shares of common stock subject to currently exercisable
    options held by Mr. Felsenthal.

(4) Includes 24,500 shares of common stock subject to currently exercisable
    options held by Dr. Holber.

                                       7
<PAGE>

                              PLAN OF DISTRIBUTION

   In addition to covering the resale of the above mentioned shares of common
stock, this prospectus covers an indeterminate number of additional shares of
common stock as may from time to time become issuable as a result of any stock
split, stock dividend, recapitalization, combination, merger, consolidation,
distribution or other similar transactions with respect to the 325,873 shares
of common stock discussed above.

   The common stock was originally issued to the selling stockholders pursuant
to exemptions from the registration requirements under Sections 4(2) or 3(a)(9)
of the Securities Act or otherwise. Of the 325,873 shares, 310,594 shares were
issued to stockholders of Klee Corporation, in exchange for their shares of
Klee Corporation, which we acquired in April 1999 (the "Klee Transaction"). The
remaining 15,279 shares were issued to three non-executive employees. In
accordance with registration rights granted to certain of the selling
stockholders in the Klee Transaction, we have filed a Registration Statement on
Form S-3 with the SEC in order to register the securities under the Securities
Act of 1933. The Registration Statement covers the resale of the 325,873 shares
of common stock from time to time on the NASDAQ National Market or in
privately-negotiated transactions. This prospectus forms a part of the
Registration Statement. We have also agreed to prepare and file such amendments
and supplements to the Registration Statement as may be necessary to keep the
Registration Statement effective until the later of one year after the date
that the Registration Statement is declared effective and the date when the
securities covered by the Registration Statement have been sold or may be sold
under SEC Rule 144(k) without volume restrictions. We have agreed to pay all
reasonable fees and expenses for the registration of the common stock. We have
agreed to indemnify the selling stockholders against certain losses, claims,
damages and liabilities, including liabilities under the Securities Act, that
could arise in connection with the selling stockholders' sales of their
securities.

   The 325,873 shares of our common stock offered in this prospectus may be
offered and sold from time to time by the selling stockholders, or by pledgees,
donees, transferees or other successors in interest. Such offers and sales may
be made from time to time on a stock exchange, market or trading facility on
which the securities are traded or in private negotiated transactions. These
sales may be at prices and on terms prevailing in the market, at prices related
to the market price of our common stock or at negotiated prices. The selling
stockholders may use any one or more of the following methods when selling the
securities:

  . ordinary brokerage transactions and transactions in which the broker-
    dealer solicits purchasers;

  . block trades in which the broker-dealer will attempt to sell the shares
    as agent but may position and resell a portion of the block as principal
    to facilitate the transaction;

  . purchases by a broker-dealer as principal and resale by the broker-dealer
    for its account,

  . an exchange distribution in accordance with the rules of the relevant
    exchange;

  . privately negotiated transactions;

  . short sales;

  . broker-dealers may agree with the selling stockholders to sell a
    specified number of such shares at a stipulated price per share;

  . a combination of any such methods of sale; and

  . any other method permitted by law.

   The selling stockholders may also sell shares under Rule 144 under the
Securities Act of 1933, if available, rather than under this prospectus.

   From time to time the selling stockholders may engage in short sales, short
sales against the box, puts and calls and other transactions in our securities,
and may sell and deliver the securities in connection with those transactions.
The selling stockholders may pledge their shares to their brokers under the
margin provisions of

                                       8
<PAGE>

their customer agreements. If a selling stockholder defaults on a margin loan,
the broker may offer and sell the pledged securities from time to time.

   Broker-dealers engaged by the selling stockholders may arrange for other
brokers-dealers to participate in sales. Broker-dealers may receive commissions
or discounts from the selling stockholders (or, if any broker-dealer acts as
agent for the purchaser of shares, from the purchaser) in amounts to be
negotiated. The selling stockholders do not expect these commissions and
discounts to exceed what is customary in the types of transactions involved.

   The selling stockholders and any broker-dealers or agents that are involved
in selling the securities may be considered to be "underwriters" within the
meaning of the Securities Act of 1933 in connection with such sales. If so, any
commissions received by such broker-dealers or agents and any profit on the
resale of the securities purchased by them may be considered to be underwriting
commissions or discounts under the Securities Act.

   In order to comply with the securities laws of some states, the securities
must be offered or sold only through registered or licensed brokers or dealers.
In addition, in some states, the securities may not be offered or sold unless
they have been registered or qualified for sale in that particular state or
unless an exemption from the registration or qualification requirement is
available and is complied with.

   Under the Securities Exchange Act of 1934, any person engaged in the
distribution of the common stock may not at the same time engage in market-
making activities with respect to the common stock for five business days prior
to the start of the distribution. In addition, each selling stockholder and any
other person participating in a distribution will be subject to the Exchange
Act, which may limit the timing of purchases and sales of securities by the
selling stockholder or any other person. These factors may affect the
marketability of the securities and the ability of brokers or dealers to engage
in market-making activities.

   All proceeds from sales of the 325,873 shares of common stock offered in the
prospectus will be the property of the selling stockholders, each of whom will
bear the expense of underwriting discounts and selling commissions, if any, and
their own legal fees.

                            LEGALITY OF COMMON STOCK

   The validity of the securities offered in this prospectus is being passed
upon for us by Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C., Boston,
Massachusetts.

                                    EXPERTS

   The financial statements incorporated in this prospectus by reference to the
Company's Annual Report on Form 10-K for the fiscal year ended June 26, 1999
have been so incorporated in reliance on the report of KPMG LLP, independent
accountants, given on the authority of said firm as experts in auditing and
accounting.

                                INDEMNIFICATION

   Section 145 of the General Corporation Law of the State of Delaware provides
that we have the power to indemnify our directors, officers, employees or
agents and certain other persons serving at our request in related capacities
against amounts paid and expenses incurred in connection with an action or
proceeding to which he or she is or is threatened to be made a party by reason
of such position, if such person shall have acted in good faith and in a manner
he reasonably believed to be in or not opposed to our best interests, and, in
any criminal proceeding, if such person had no reasonable cause to believe his
conduct was unlawful, provided that, in the

                                       9
<PAGE>

case of actions brought by or on behalf of us, no indemnification shall be made
with respect to any matter as to which such person shall have been adjudged to
be liable to us unless and only to the extent that the adjudicating court
determines that such indemnification is proper under the circumstances.

   Section 102(b)(7) of the Delaware General Corporation Law permits us to
provide in our certificate of incorporation that our directors shall not be
personally liable to us or our stockholders for monetary damages for breach of
fiduciary duty as a director, except for liability (i) for any breach of the
director's duty of loyalty to the corporation or its stockholders, (ii) for
acts or omissions not in good faith or which involve intentional misconduct or
a knowing violation of law, (iii) under Section 174 of the Delaware General
Corporation Law, or (iv) for any transaction from which the director derived an
improper personal benefit.

   Our Restated Certificate of Incorporation provides for indemnification to
the fullest extent permitted by law and that we may advance litigation expenses
to an officer or director prior to the final disposition of an action.

   Our Certificate of Incorporation also provides, as permitted by Delaware
law, that directors shall not be personally liable to us or our stockholders
for monetary damages for breach of fiduciary duty as a director, except for
liability (i) for any breach of a director's duty of loyalty to the Company or
its stockholders, (ii) for acts or omissions not in good faith or which involve
intentional misconduct or knowing violations of law, (iii) under Section 174 of
the Delaware General Corporation Law or (iv) for any transaction from which the
director derived an improper personal benefit.

   We have a Directors and Officers liability insurance policy that insures our
officers and directors against certain liabilities.

Commission Policy

   Insofar as indemnification for liabilities arising under the Securities Act
may be permitted to directors, officers or persons controlling us, we have been
informed that in the opinion of the SEC such indemnification is against public
policy as expressed in the Securities Act and is therefore unenforceable.

                                       10
<PAGE>

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

   You should rely only on the information contained in this prospectus. We
have not authorized anyone to provide you with information different from that
contained in this prospectus. The selling stockholders are offering to sell
and seeking offers to buy shares of our common stock and warrants only in
jurisdictions where offers and sales are permitted. The information contained
in this prospectus is accurate only as of October 25, 1999. You should not
assume that this prospectus is accurate as of any other date.

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

                               TABLE OF CONTENTS

<TABLE>
<CAPTION>
                                                                            Page
                                                                            ----
<S>                                                                         <C>
Where You Can Find More Information........................................   2
Incorporation of Certain Information by
 Reference.................................................................   2
The Company................................................................   3
Use of Proceeds............................................................   5
Description of Securities..................................................   5
Transfer Agent and Registrar...............................................   6
Selling Stockholders.......................................................   7
Plan of Distribution.......................................................   8
Legality of Common Stock...................................................   9
Experts....................................................................   9
Indemnification............................................................   9
</TABLE>

-------------------------------------------------------------------------------
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                        325,873 Shares of Common Stock,
                           $.01 par value per share

                     APPLIED SCIENCE AND TECHNOLOGY, INC.

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

                                  PROSPECTUS

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

                               October 25, 1999

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

                PART II. INFORMATION NOT REQUIRED IN PROSPECTUS

Item 14. Other Expenses of Issuance and Distribution.

   The table sets forth our estimates (other than the SEC and NASDAQ filing
fees) of our expenses in connection with the issuance and distribution of the
common stock being registered. None of the following expenses are being paid by
the selling stockholders.

<TABLE>
<CAPTION>
   Item                                                                Amount
   ----                                                              ----------
   <S>                                                               <C>
   SEC registration fee............................................. $ 2,162.90
   NASDAQ Listing Fee...............................................   6,000.00
   Legal fees and expenses..........................................   6,000.00
   Accounting fees and expenses.....................................   2,500.00
   Miscellaneous fees and expenses..................................   5,000.00
                                                                     ----------
     Total.......................................................... $21,662.90
                                                                     ==========
</TABLE>

   The selling stockholders will bear the expense of their own legal counsel
for the registration of the securities being registered and miscellaneous fees
and expenses, if any.

Item 15. Indemnification of Directors and Officers.

   See "Indemnification" contained in Part I hereof, which is incorporated
herein by reference.

Item 16. Exhibits.

<TABLE>
<CAPTION>
   Exhibit
   Number                               Description
   -------                              -----------
   <C>     <S>
     4.1   The Restated Certificate of Incorporation of the Registrant
           (previously filed as Exhibit 3a to the Registrant's Registration
           Statement on Form SB-2, File No. 33-69098-B, and incorporated herein
           by reference).
     4.2   Form of Common Stock Certificate (previously filed as Exhibit No. 4a
           to the Registrant's Registration Statement on Form SB-2, File No.
           33-69098-B, and incorporated herein by reference).
     5     Opinion of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C., with
           respect to the legality of the securities being registered.
    23.1   Consent of KPMG LLP.
    23.2   Consent of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.
           (included in Exhibit 5).
    24     Power of Attorney (filed in Part II of this Registration Statement).
</TABLE>

Item 17. Undertakings.

 A. Rule 415 Offering

   The undersigned registrant hereby undertakes:

   (1) To file, during any period in which offers or sales are being made, a
post-effective amendment to this registration statement:

  (i) To include any prospectus required by Section 10(a)(3) of the
      Securities Act;

  (ii) To reflect in the prospectus any facts or events arising after the
       effective date of the registration statement (or the most recent post-
       effective amendment thereof) which, individually or in the

                                      II-1
<PAGE>

     aggregate, represent a fundamental change in the information set forth
     in the registration statement. Notwithstanding the foregoing, any
     increase or decrease in volume of securities offered (if the total
     dollar value of securities offered would not exceed that which was
     registered) and any deviation from the low or high end of the estimated
     maximum offering range may be reflected in the form of prospectus filed
     with the Commission pursuant to Rule 424(b)(sec.230.424(b) of this
     chapter) if, in the aggregate, the changes in volume and price represent
     no more than a 20% change in the maximum aggregate offering price set
     forth in the "Calculation of Registration Fee" table in the effective
     registration statement.

  (iii) To include any material information with respect to the plan of
        distribution not previously disclosed in the registration statement
        or any material change to such information in the registration
        statement;

Provided, however, that paragraphs (A)(1)(i) and (A)(1)(ii) do not apply if
the registration statement is on Form S-3 or Form S-8, and the information
required to be included in a post-effective amendment by those paragraphs is
contained in periodic reports filed by the Registrant pursuant to Section 13
or Section 15(d) of the 1934 Act that are incorporated by reference in the
registration statement.

   (2) That, for the purpose of determining any liability under the Securities
Act, each such post-effective amendment 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.

   (3) To remove from registration by means of a post-effective amendment any
of the securities being registered which remain unsold at the termination of
the offering.

 B. Filings Incorporating Subsequent Exchange Act Documents by Reference

   The undersigned registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act of 1933, 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.

 C. Incorporated Annual and Quarterly Reports.

   The undersigned registrant hereby undertakes to deliver or cause to be
delivered with the prospectus, to each person to whom the prospectus is sent
or given, the latest annual report to security holders that is incorporated by
reference in the prospectus and furnished pursuant to and meeting the
requirements of Rule 14a-3 or Rule 14c-3 under the Securities Exchange Act of
1934; and, where interim financial information required to be presented by
Article 3 of Regulation S-X is not set forth in the prospectus, to deliver, or
cause to be delivered to each person to whom the prospectus is sent or given,
the latest quarterly report that is specifically incorporated by reference in
the prospectus to provide such interim financial information.

 D. Request for Acceleration of Effective Date or Filing of Registration
 Statement on Form S-8

   Insofar as indemnification for liabilities arising under the Securities Act
of 1933 may be permitted to 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 Securities and Exchange Commission
such indemnification is against public policy as expressed in the Securities
Act of 1933 and is, therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by

                                     II-2
<PAGE>

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 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.

                                      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 Woburn, Commonwealth of Massachusetts, on October
25, 1999

                                          APPLIED SCIENCE AND TECHNOLOGY, INC.

                                               /s/ Richard S. Post, Ph.D.
                                          By: _________________________________
                                                   Richard S. Post, Ph.D.
                                                  Chief Executive Officer

                               POWER OF ATTORNEY

   KNOW ALL MEN BY THESE PRESENTS, that each person whose signature appears
below constitutes and appoints Richard S. Post, Ph.D. and John M. Tarrh, or any
of them, his attorney-in-fact, each with the power of substitution, for him in
any and all capacities, to sign any and all amendments (including
post-effective amendments) to this registration statement, (or any other
registration statement for the same offering that is to be effective upon
filing pursuant to Rule 462(b) under the Securities Act) and to file the same,
with all exhibits thereto and other documents in connection therewith, with the
Securities and Exchange Commission, hereby granting unto said attorneys-in-fact
and agents, and each of them, full power and authority to do and perform each
and every act and thing requisite or necessary to be done in and about the
premises, as full to all intents and purposes as he might or could do in
person, hereby ratifying and confirming all that said attorneys-in-fact and
agents or any of them or their or his substitutes may lawfully do or cause to
be done by virtue hereof.

   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/ Richard S. Post, Ph.D.         Chief Executive Officer     October 25, 1999
______________________________________  and Chairman of the Board
        Richard S. Post, Ph.D.          (principal executive
                                        officer)

        /s/ John M. Tarrh              Senior VicePresident,       October 25, 1999
______________________________________  Finance and Director
            John M. Tarrh               (principal financial
                                        officer and principal
                                        accounting officer)

      /s/ Robert R. Anderson           Director                    October 25, 1999
______________________________________
          Robert R. Anderson

      /s/ Michel de Beaumont           Director                    October 25, 1999
______________________________________
          Michel de Beaumont
</TABLE>

                                      II-4
<PAGE>

<TABLE>
<CAPTION>
              Signature                          Title                   Date
              ---------                          -----                   ----
<S>                                    <C>                        <C>
       /s/ John R. Bertucci            Director                    October 25, 1999
______________________________________
           John R. Bertucci

       /s/ Hans-Jochen Kahl            Director                    October 25, 1999
______________________________________
           Hans-Jochen Kahl

    /s/ Donald K. Smith, Ph.D.         Director                    October 25, 1999
______________________________________
        Donald K. Smith, Ph.D.
</TABLE>

                                      II-5
<PAGE>

                      APPLIED SCIENCE AND TECHNOLOGY, INC.

                          INDEX TO EXHIBITS FILED WITH
                        FORM S-3 REGISTRATION STATEMENT

<TABLE>
<CAPTION>
   Exhibit
   Number                               Description
   -------                              -----------
   <C>     <S>
     4.1   The Certificate of Incorporation of the Registrant (previously filed
           as Exhibit 3a to the Registrant's Registration Statement on Form SB-
           2, File No. 33-69098-B, and incorporated herein by reference).
     4.2   Form of Common Stock Certificate (previously filed as Exhibit No. 4a
           to the Registrant's Registration Statement on Form SB-2, File No.
           33-69098-B, and incorporated herein by reference).
     5     Opinion of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C., with
           respect to the legality of the securities being registered.
    23.1   Consent of KPMG LLP.
    23.2   Consent of Mintz, Levin, Cohn, Ferris, Glovsky and Popeo, P.C.
           (included in Exhibit 5)
    24     Power of Attorney (filed in Part II of this Registration Statement).
</TABLE>