Exhibit 3.18

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                              AMENDED AND RESTATED

                                     BY-LAWS

                                       OF

                           DRUG-FREE CONSORTIUM, INC.

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                       Incorporated under the Laws of the

                                 State of Texas

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                                  Adopted as of
                                 August 17, 1999

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                              AMENDED AND RESTATED

                                     BY-LAWS

                                       OF

                           DRUG-FREE CONSORTIUM, INC.

                              (a Texas corporation)

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                                    ARTICLE I

                                     OFFICES

               The  registered  office of the  Corporation in the State of Texas
shall be located in the City of Seattle,  County of King.  The  Corporation  may
establish  or  discontinue,  from time to time,  such  other  offices  within or
without  the  State of Texas as may be  deemed  proper  for the  conduct  of the
Corporation's business.

                                   ARTICLE II

                            MEETINGS OF STOCKHOLDERS

               SECTION 1. PLACE OF MEETINGS.  All meetings of stockholders shall
be held at such place or places,  within or without  the State of Texas,  as may
from time to time be fixed by the Board of  Directors,  or as shall be specified
in the respective notices, or waivers of notice, thereof.

               SECTION 2. ANNUAL MEETING. The annual meeting of stockholders for
the election of Directors and the transaction of other business shall be held on
such date and at such place as may be designated  by the Board of Directors.  At
each  annual  meeting the  stockholders  entitled

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to vote shall elect a Board of  Directors  and may  transact  such other  proper
business as may come before the meeting.

               SECTION  3.   SPECIAL   MEETINGS.   A  special   meeting  of  the
stockholders,  or of any class  thereof  entitled  to vote,  for any  purpose or
purposes, may be called at any time by the Chairman of the Board, if any, or the
President  or by order of the  Board of  Directors  and  shall be  called by the
Secretary upon the written  request of  stockholders  holding of record at least
50% of the outstanding  shares of stock of the  Corporation  entitled to vote at
such meeting. Such written request shall state the purpose or purposes for which
such meeting is to be called.

               SECTION 4. NOTICE OF MEETINGS.  Except as  otherwise  provided by
law, written notice of each meeting of stockholders,  whether annual or special,
stating the place, date and hour of the meeting shall be given not less than ten
days or more than sixty days  before the date on which the meeting is to be held
to each  stockholder  of record  entitled to vote thereat by delivering a notice
thereof  to him  personally  or by  mailing  such  notice in a  postage  prepaid
envelope  directed  to him at his  address as it  appears on the  records of the
Corporation,  unless he shall have filed with the Secretary of the Corporation a
written request that notices intended for him be directed to another address, in
which case such notice  shall be directed  to him at the address  designated  in
such request.  Notice shall not be required to be given to any  stockholder  who
shall waive such notice in writing,  whether prior to or after such meeting,  or
who shall attend such meeting in person or by proxy  unless such  attendance  is
for the express purpose of objecting,  at the beginning of such meeting,  to the
transactions  of any  business  because  the meeting is not  lawfully  called or
convened.  Every notice of a special  meeting of the  stockholders,  besides the
time and place of the  meeting,  shall  state  briefly  the  objects or purposes
thereof.

               SECTION  5.  LIST OF  STOCKHOLDERS.  It  shall be the duty of the
Secretary or other officer of the Corporation who shall have charge of the stock
ledger to  prepare  and make,  at least ten days  before  every  meeting  of the
stockholders,  a complete  list of the  stockholders  entitled to vote  thereat,
arranged in alphabetical  order, and showing the address of each stockholder and
the  number of shares  registered  in his name.  Such list  shall be open to the
examination of any stockholder,  for any purpose germane to the meeting,  during
ordinary business hours, for a period of at least ten days prior to the meeting,
either at a place  within the city where the meeting is to be held,  which place
shall be specified in the notice of the meeting, or, if not so specified, at the
place  where the meeting is to be held.  The list shall be kept and  produced at
the time and place of the meeting  during the whole time  thereof and subject to
the inspection of any stockholder who may be present.  The original or duplicate
ledger  shall be the only  evidence as to who are the  stockholders  entitled to
examine  such  list or the books of the  Corporation  or to vote in person or by
proxy at such meeting.

               SECTION  6.  QUORUM.  At each  meeting of the  stockholders,  the
holders of record of a  majority  of the  issued  and  outstanding  stock of the
Corporation  entitled  to vote at such  meeting,  present in person or by proxy,
shall  constitute  a  quorum  for the  transaction  of  business,  except  where
otherwise provided by law, the Certificate of Incorporation or these By-laws. In

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the absence of a quorum, any officer entitled to preside at, or act as Secretary
of, such  meeting  shall have the power to adjourn the meeting from time to time
until a quorum shall be constituted.

               SECTION 7. VOTING. Every stockholder of record who is entitled to
vote shall at every meeting of the stockholders be entitled to one vote for each
share of stock held by him on the record date; EXCEPT,  HOWEVER,  that shares of
its own stock  belonging  to the  Corporation  or to another  corporation,  if a
majority of the shares  entitled to vote in the  election of  directors  of such
other corporation is held by the Corporation,  shall neither be entitled to vote
nor counted for quorum  purposes.  Nothing in this Section shall be construed as
limiting  the right of the  Corporation  to vote its own  stock  held by it in a
fiduciary capacity. At all meetings of the stockholders, a quorum being present,
all matters shall be decided by majority vote of the shares of stock entitled to
vote held by  stockholders  present in person or by proxy,  except as  otherwise
required  by law or the  Certificate  of  Incorporation.  Unless  demanded  by a
stockholder of the  Corporation  present in person or by proxy at any meeting of
the  stockholders and entitled to vote thereat or so directed by the chairman of
the meeting or required by law, the vote thereat on any question  need not be by
written ballot. On a vote by written ballot,  each ballot shall be signed by the
stockholder  voting,  or in his name by his proxy,  if there be such proxy,  and
shall  state the number of shares  voted by him and the number of votes to which
each share is entitled.

               SECTION  8.  PROXIES.  Each  stockholder  entitled  to  vote at a
meeting of  stockholders  or to express  consent to corporate  action in writing
without a meeting  may  authorize  another  person or  persons to act for him by
proxy.  A proxy  acting  for any  stockholder  shall  be  duly  appointed  by an
instrument in writing  subscribed by such  stockholder.  No proxy shall be valid
after the  expiration  of three  years  from the date  thereof  unless the proxy
provides for a longer period.

               SECTION 9. ACTION  WITHOUT A MEETING.  Any action  required to be
taken at any annual or special  meeting of  stockholders or any action which may
be taken at any annual or special meeting of stockholders may be taken without a
meeting,  without  prior  notice  and  without a vote,  if a consent  in writing
setting forth the action so taken shall be signed by the holders of  outstanding
stock  having not less than the minimum  number of votes that would be necessary
to  authorize  or take such action at a meeting at which all shares  entitled to
vote  thereon  were  present  and  voted.  Prompt  notice  of the  taking of the
corporate action without a meeting by less than unanimous  written consent shall
be given to those stockholders who have not consented in writing.

                                   ARTICLE III

                               BOARD OF DIRECTORS

               SECTION 1. POWERS.  The  business and affairs of the  Corporation
shall be managed under the direction of the Board of Directors.


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               SECTION 2.  ELECTION AND TERM.  Except as  otherwise  provided by
law,  Directors shall be elected at the annual meeting of stockholders and shall
hold  office  until the next  annual  meeting of  stockholders  and until  their
successors  are elected  and  qualify,  or until they sooner die,  resign or are
removed.  At each annual meeting of stockholders,  at which a quorum is present,
the  persons  receiving a  plurality  of the votes cast shall be the  Directors.
Acceptance of the office of Director may be expressed orally or in writing,  and
attendance at the organization meeting shall constitute such acceptance.

               SECTION 3. NUMBER.  The number of Directors  shall be such number
as shall be determined from time to time by the Board of Directors and initially
shall be two.

               SECTION 4. QUORUM AND MANNER OF ACTING. Unless otherwise provided
by law, the  presence of 50% of the whole Board of Directors  shall be necessary
to  constitute a quorum for the  transaction  of  business.  In the absence of a
quorum, a majority of the Directors present may adjourn the meeting from time to
time until a quorum shall be present.  Notice of any adjourned  meeting need not
be given.  At all meetings of  Directors,  a quorum being  present,  all matters
shall be decided by the affirmative vote of a majority of the Directors present,
except  as  otherwise  required  by law.  The  Board of  Directors  may hold its
meetings  at such place or places  within or  without  the State of Texas as the
Board of Directors  may from time to time  determine or as shall be specified in
the respective notices, or waivers of notice, thereof.

               SECTION 5.  ORGANIZATION  MEETING.  Immediately after each annual
meeting of  stockholders  for the election of  Directors  the Board of Directors
shall meet at the place of the annual meeting of stockholders for the purpose of
organization,  the election of officers and the  transaction of other  business.
Notice of such meeting  need not be given.  If such meeting is held at any other
time or place, notice thereof must be given as hereinafter  provided for special
meetings of the Board of Directors,  subject to the execution of a waiver of the
notice  thereof  signed by, or the  attendance at such meeting of, all Directors
who may not have received such notice.

               SECTION 6.  REGULAR  MEETINGS.  Regular  meetings of the Board of
Directors  may be held at such place,  within or without the State of Texas,  as
shall from time to time be determined by the Board of Directors. After there has
been such  determination,  and notice thereof has been once given to each member
of the Board of Directors as hereinafter provided for special meetings,  regular
meetings may be held without further notice being given.

               SECTION 7.  SPECIAL  MEETINGS;  NOTICE.  Special  meetings of the
Board of Directors  shall be held whenever  called by the Chairman of the Board,
if any,  the  President or by a majority of the  Directors.  Notice of each such
meeting shall be mailed to each  Director,  addressed to him at his residence or
usual place of business, at least five days before the date on which the meeting
is to be held, or shall be sent to him at such place by telex or  facsimile,  or
be delivered  personally or by telephone,  not later than the day before the day
on which such  meeting is to be held.  Each such notice shall state the time and
place of the meeting and, as may be required,  the


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purposes  thereof.  Notice of any meeting of the Board of Directors  need not be
given to any Director if he shall sign a written waiver thereof either before or
after the time stated therein for such meeting, or if he shall be present at the
meeting. Unless limited by law, the Certificate of Incorporation,  these By-laws
or the terms of the notice  thereof,  any and all business may be  transacted at
any meeting  without  the notice  thereof  having  specifically  identified  the
matters to be acted upon.

               SECTION 8. REMOVAL OF DIRECTORS. Any Director or the entire Board
of Directors may be removed,  with or without  cause,  at any time, by action of
the holders of record of the majority of the issued and outstanding stock of the
Corporation  (a)  present  in person or by proxy at a meeting of holders of such
stock and  entitled to vote thereon or (b) by a consent in writing in the manner
contemplated  in Section 9 of Article  II, and the vacancy or  vacancies  in the
Board of Directors  caused by any such removal may be filled by action of such a
majority at such meeting or at any subsequent meeting or by consent.

               SECTION 9.  RESIGNATIONS.  Any  Director of the  Corporation  may
resign at any time by giving  written  notice to the  Chairman of the Board,  if
any, the President, the Vice President or the Secretary of the Corporation.  The
resignation  of any Director shall take effect upon receipt of notice thereof or
at such later time as shall be specified in such notice;  and, unless  otherwise
specified therein,  the acceptance of such resignation shall not be necessary to
make it effective.

               SECTION  10.  VACANCIES.  Any  newly  created  directorships  and
vacancies  occurring in the Board by reason of death,  resignation,  retirement,
disqualification or removal,  with or without cause, may be filled by the action
of the holders of record of the majority of the issued and outstanding  stock of
the  Corporation  (a)  present  in person or by proxy at a meeting of holders of
such stock and  entitled  to vote  thereon or (b) by a consent in writing in the
manner contemplated in Section 9 of Article II. The Director so chosen,  whether
selected to fill a vacancy or elected to a new  directorship,  shall hold office
until the next meeting of  stockholders at which the election of Directors is in
the regular  order of  business,  and until his  successor  has been elected and
qualifies, or until he sooner dies, resigns or is removed.

               SECTION 11. COMPENSATION OF DIRECTORS.  Directors, as such, shall
not receive any stated  salary for their  services,  but, by  resolution  of the
Board,  a specific  sum fixed by the Board  plus  expenses  may be  allowed  for
attendance at each regular or special meeting of the Board;  PROVIDED,  HOWEVER,
that nothing herein  contained  shall be construed to preclude any Director from
serving the Corporation or any parent or subsidiary  corporation  thereof in any
other capacity and receiving compensation therefor.

               SECTION  12.  ACTION  WITHOUT A MEETING.  Any action  required or
permitted  to be taken at any  meeting  of the Board of  Directors  may be taken
without a meeting if a written  consent  thereto is signed by all members of the
Board,  and such written consent is filed with the minutes or proceedings of the
Board.

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               SECTION 13. TELEPHONIC PARTICIPATION IN MEETINGS.  Members of the
Board  of  Directors  may  participate  in a  meeting  of the  Board by means of
conference telephone or similar  communications  equipment by means of which all
persons participating in the meeting can hear each other, and such participation
shall constitute presence in person at such meeting.

                                   ARTICLE IV

                                    OFFICERS

               SECTION 1. PRINCIPAL OFFICERS. The Board of Directors shall elect
a President,  a Secretary and a Treasurer,  and may in addition elect a Chairman
of the Board,  one or more Vice  Presidents  and such other officers as it deems
fit; the President,  the Secretary, the Treasurer, the Chairman of the Board (if
any) and the Vice  Presidents  (if any)  being  the  principal  officers  of the
Corporation.  One person may hold, and perform the duties of, any two or more of
said offices.

               SECTION 2. ELECTION AND TERM OF OFFICE. The principal officers of
the  Corporation  shall be elected  annually  by the Board of  Directors  at the
organization  meeting  thereof.  Each such  officer  shall hold office until his
successor shall have been elected and shall qualify, or until his earlier death,
resignation or removal.

               SECTION 3. OTHER OFFICERS.  In addition,  the Board may elect, or
the Chairman of the Board,  if any, or the  President  may  appoint,  such other
officers  as they  deem  fit.  Any such  other  officers  chosen by the Board of
Directors  shall be subordinate  officers and shall hold office for such period,
have such  authority  and  perform  such duties as the Board of  Directors,  the
Chairman of the Board, if any, or the President may from time to time determine.

               SECTION 4.  REMOVAL.  Any officer may be removed,  either with or
without cause,  at any time, by resolution  adopted by the Board of Directors at
any regular  meeting of the Board, or at any special meeting of the Board called
for that purpose, at which a quorum is present.

               SECTION 5.  RESIGNATIONS.  Any  officer may resign at any time by
giving written notice to the Chairman of the Board,  if any, the President,  the
Secretary or the Board of Directors. Any such resignation shall take effect upon
receipt  of such  notice or at any later time  specified  therein;  and,  unless
otherwise  specified  therein,  the acceptance of such resignation  shall not be
necessary to make it effective.

               SECTION 6.  VACANCIES.  A vacancy in any office may be filled for
the unexpired  portion of the term in the manner prescribed in these By-laws for
election or appointment to such office for such term.

               SECTION 7.  CHAIRMAN OF THE BOARD.  The  Chairman of the Board of
Directors,  if one be elected,  shall  preside if present at all meetings of the
Board of Directors, and he shall have and perform such other duties as from time
to time may be assigned to him by the Board of Directors.


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               SECTION 8. PRESIDENT.  The President shall be the chief operating
officer  of the  Corporation  and shall  have the  general  powers and duties of
supervision  and  management  usually  vested in the  office of  president  of a
corporation.  He shall  preside at all meetings of the  stockholders  if present
thereat,  and in the  absence or  non-election  of the  Chairman of the Board of
Directors,  at all  meetings of the Board of  Directors,  and shall have general
supervision, direction and control of the business of the Corporation. Except as
the Board of  Directors  shall  authorize  the  execution  thereof in some other
manner, he shall execute bonds, mortgages,  and other contracts on behalf of the
Corporation,  and shall cause the seal to be affixed to any instrument requiring
it and when so  affixed  the seal  shall be  attested  by the  signature  of the
Secretary or the Treasurer.

               SECTION  9.  VICE  PRESIDENT.  Each  Vice  President,  if such be
elected,  shall  have such  powers  and shall  perform  such  duties as shall be
assigned to him by the President or the Board of Directors.

               SECTION  10.  TREASURER.  The  Treasurer  shall  have  charge and
custody of, and be responsible for, all funds and securities of the Corporation.
He shall exhibit at all reasonable times his books of account and records to any
of the Directors of the Corporation  upon  application  during business hours at
the office of the  Corporation  where such books and records shall be kept; when
requested  by the  Board of  Directors,  he  shall  render  a  statement  of the
condition of the finances of the  Corporation  at any meeting of the Board or at
the annual  meeting of  stockholders;  he shall  receive,  and give receipt for,
moneys  due and  payable  to the  Corporation  from any  source  whatsoever;  in
general, he shall perform all the duties incident to the office of Treasurer and
such other duties as from time to time may be assigned to him by the Chairman of
the Board of Directors,  the President or the Board of Directors.  The Treasurer
shall give such bond,  if any, for the  faithful  discharge of his duties as the
Board of Directors may require.

               SECTION 11. SECRETARY.  The Secretary,  if present,  shall act as
secretary at all meetings of the Board of Directors and of the  stockholders and
keep the minutes thereof in a book or books to be provided for that purpose;  he
shall see that all  notices  required  to be given by the  Corporation  are duly
given and served;  he shall have charge of the stock records of the Corporation;
he shall see that all reports,  statements and other  documents  required by law
are  properly  kept and filed;  and in general he shall  perform  all the duties
incident to the office of  Secretary  and such other duties as from time to time
may be assigned to him by the President or the Board of Directors.

               SECTION 12.  SALARIES.  The  salaries of the  principal  officers
shall be fixed from time to time by the Board of Directors,  and the salaries of
any other officers may be fixed by the President.

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                                    ARTICLE V

                    INDEMNIFICATION OF OFFICERS AND DIRECTORS

               SECTION  1.  RIGHT  OF  INDEMNIFICATION.   Every  person  now  or
hereafter  serving as a Director  or officer of the  Corporation  and every such
Director  or officer  serving at the request of the  Corporation  as a director,
officer, employee or agent of another corporation,  partnership,  joint venture,
trust or other enterprise, shall be indemnified by the Corporation in accordance
with and to the  fullest  extent  permitted  by law for the  defense  of,  or in
connection  with,  any  threatened,   pending  or  completed  action,   suit  or
proceeding, whether civil, criminal, administrative or investigative.

               SECTION 2.  EXPENSES.  Expenses  incurred in defending a civil or
criminal action, suit or proceeding may be paid by the Corporation in advance of
the final  disposition  of such action,  suit or proceeding as authorized by the
Board of Directors in the specific case upon receipt of an  undertaking by or on
behalf  of such  Director  or  officer  to repay  such  amount  unless  it shall
ultimately  be  determined  that  he  is  entitled  to  be  indemnified  by  the
Corporation as authorized in this Article V.

               SECTION  3.  OTHER  RIGHTS  OF  INDEMNIFICATION.   The  right  of
indemnification  herein  provided  shall  not be deemed  exclusive  of any other
rights to which any such  Director or officer may now or  hereafter  be entitled
under any by-law,  agreement, vote of stockholders or disinterested directors or
otherwise,  both as to  action  in his  official  capacity  and as to  action in
another  capacity  while holding such office,  and shall continue as to a person
who has ceased to be a Director or officer and shall inure to the benefit of the
heirs, executors and administrators of such person.

                                   ARTICLE VI

                            SHARES AND THEIR TRANSFER

               SECTION  1.  CERTIFICATE  FOR  STOCK.  Every  stockholder  of the
Corporation  shall be entitled to a certificate or  certificates,  to be in such
form as the Board of Directors shall prescribe,  certifying the number of shares
of the capital stock of the  Corporation  owned by him. No certificate  shall be
issued for partly paid shares.

               SECTION 2. STOCK CERTIFICATE SIGNATURE. The certificates for such
stock  shall be numbered in the order in which they shall be issued and shall be
signed by the  Chairman  of the  Board,  if any,  or the  President  or any Vice
President and by the Secretary or an Assistant Secretary or the Treasurer of the
Corporation,  and its seal  shall be affixed  thereto.  If such  certificate  is
countersigned  (1)  by a  transfer  agent  other  than  the  Corporation  or its
employee, or, (2) by a registrar other than the Corporation or its employee, the
signatures of such officers of the  Corporation  may be facsimiles.  In case any
officer of the Corporation who has signed, or whose facsimile signature has been
placed upon,  any such  certificate  shall have ceased to be such

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officer before such  certificate is issued,  it may be issued by the Corporation
with the same effect as if he were such officer at the date of issue.

               SECTION 3. STOCK LEDGER.  A record shall be kept by the Secretary
or by any other officer,  employee or agent designated by the Board of Directors
of the name of each person,  firm or  corporation  holding  capital stock of the
Corporation,  the number of shares  represented by, and the respective dates of,
each certificate for such capital stock, and in case of cancellation of any such
certificate, the respective dates of cancellation.

                                   ARTICLE VII

                            MISCELLANEOUS PROVISIONS

               SECTION 1. CORPORATE SEAL. The Board of Directors shall provide a
corporate  seal,  which  shall be in such  form as the  Board of  Directors  may
decide. The Secretary shall be the custodian of the seal. The Board of Directors
may authorize a duplicate seal to be kept and used by any other officer.

               SECTION 2. VOTING OF STOCKS OWNED BY THE  CORPORATION.  The Board
of Directors may authorize  any person on behalf of the  Corporation  to attend,
vote  and  grant  proxies  to be  used at any  meeting  of  stockholders  of any
corporation (except the Corporation) in which the Corporation may hold stock.

               SECTION  3.   DIVIDENDS.   Subject  to  the   provisions  of  the
Certificate of  Incorporation,  the Board of Directors may, out of funds legally
available therefor, at any regular or special meeting declare dividends upon the
capital  stock  of the  Corporation  as and when  they  deem  expedient.  Before
declaring  any  dividend  there  may  be set  apart  out  of  any  funds  of the
Corporation  available for dividends such sum or sums as the Directors from time
to time in their discretion deem proper for working capital or as a reserve fund
to meet contingencies or for equalizing  dividends or for such other purposes as
the Board of Directors shall deem conducive to the interests of the Corporation.

                                  ARTICLE VIII

                                   AMENDMENTS

               These  By-laws  of the  Corporation  may be  altered,  amended or
repealed  by the Board of  Directors  at any  regular or special  meeting of the
Board of  Directors  or by the  affirmative  vote of the  holders of record of a
majority of the issued and  outstanding  stock of the Corporation (i) present in
person or by proxy at a meeting of holders  of such stock and  entitled  to vote
thereon or (ii) by a consent in writing in the manner  contemplated in Section 9
of Article  II,  PROVIDED,  HOWEVER,  that  notice of the  proposed  alteration,
amendment or repeal is contained in

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the notice of such meeting. By-laws, whether made or altered by the stockholders
or by the Board of  Directors,  shall be subject to  alteration or repeal by the
stockholders as in this Article VIII above provided.

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