MEMC ELECTRONIC MATERIALS, INC.
                        SPECIAL INCENTIVE BONUS AGREEMENT

     THIS  AGREEMENT is entered into between  MEMC  Electronic  Materials,  Inc.
("MEMC") and Ralph D. Hartung ("Employee").

     Employee is employed by MEMC.

     MEMC recognizes the value of the services  performed by Employee and wishes
to encourage  Employee to continue  employment with MEMC.  Employee wishes to be
paid a certain  amount of  additional  compensation  in  return  for  continuous
employment with MEMC for a designated period of time.

     NOW,  THEREFORE,  in consideration of the mutual promises contained in this
Agreement, the parties agree as follows:

     1. Nature of Contract. This Agreement provides for an additional bonus (the
"Special  Incentive  Bonus") to be paid by MEMC to Employee in consideration for
Employee's  continuous employment throughout the period of April 1, 1998 through
June 30, 1999 (the "Retention Period").

     Nothing  contained in this Agreement shall be construed to be a contract of
employment for any term,  nor as conferring  upon Employee the right to continue
in the  employment  of MEMC  in  Employee's  present  capacity  or in any  other
capacity.  Nothing  contained in this  Agreement  shall be construed to preclude
either party from terminating the employment relationship at any time.

     It is  expressly  understood  by the parties  that this  Agreement  relates
exclusively  to  additional  compensation  for  Employee's  services  and is not
intended to be the entire employment contract. This Agreement merely supplements
Employee's employment contract with MEMC.

     The Special  Incentive  Bonus  provided by this Agreement is in addition to
the cash compensation and other fringe benefits provided to Employee pursuant to
any plan or plans maintained by MEMC for its employees generally.

     2. Special  Incentive  Bonus. If Employee remains in the employment of MEMC
continuously  throughout the Retention  Period of April 1, 1998 through June 30,
1999,  Employee shall be entitled to a Special  Incentive Bonus in the amount of
$250,000.

     3. Terms of Payment.  Fifty percent of the Special  Incentive Bonus will be
payable with the March 31, 1998 payroll (the "Advance  Payment");  the remaining
fifty percent of the Special  Incentive  Bonus will be payable with the June 30,
1999 payroll (the "Final Payment").

     Subject  to  the  exceptions  below,  in  the  event  Employee   terminates
employment  with MEMC before April 1, 1999,  Employee  shall  reimburse MEMC the
entire amount of the Advance Payment (including any payroll tax withheld).

     Subject  to  the  exceptions  below,  in  the  event  Employee   terminates
employment  with MEMC after  March 31,  1999 and before  July 1, 1999,  Employee
shall reimburse MEMC that portion of the Advance Payment  (including any payroll
tax  withheld)  that the number of days in the period  beginning  on the date of
Employee's termination of employment with MEMC and ending on June 30, 1999 bears
to 456.  For example,  if Employee  terminates  employment  with MEMC on June 1,
1999, Employee shall reimburse MEMC 30 / 456 (or 6.58%) of the Advance Payment.

     No  reimbursement  of the Advance Payment shall be required in the event of
the  death or total  and  permanent  disability  of  Employee,  or in the  event
Employee's employment with MEMC is involuntarily  terminated by MEMC as a result
of a change in control of MEMC or a  reduction  in the  workforce  of MEMC.  The
reimbursement  as described  above shall be required in the event of  Employee's
termination of employment with MEMC for any other reason.

     In no event shall Employee be entitled to the Final Payment in the event of
Employee's  termination  of  employment  with MEMC for any reason before July 1,
1999.

     4. Tax Withholding

     MEMC shall withhold from the Special  Incentive Bonus the amount  necessary
to enable MEMC to remit to the  appropriate  government  entity or entities  the
amount  required to be withheld  from wages with respect to such  payments.  All
references to the Special  Incentive Bonus,  the Advance Payment,  and the Final
Payment shall mean the gross amount of such amount before such payroll taxes are
withheld.

     5. Collection of Reimbursement

     Employee agrees that any  reimbursement  of the Advance Payment due MEMC in
the event of termination  of employment of the Employee  before July 1, 1999 may
be withheld by MEMC from any amounts owed by MEMC to Employee.

     6. Confidentiality

     Employee  agrees that the terms of this Special  Incentive  Bonus Agreement
are  confidential  and will not be discussed with or disclosed to any present or
former employee of MEMC or its affiliates or subsidiaries.

     7. Governing Law

     The  interpretation  and enforcement of this Agreement shall be governed by
the laws of the State of Missouri.

     Employee  acknowledges  that this  Agreement has been reviewed in detail by
Employee and that Employee voluntarily entered into this Agreement.

     IN WITNESS WHEREOF,  the parties have executed this Special Incentive Bonus
Agreement this 24th day of March, 1998.

                                  MEMC ELECTRONIC MATERIALS, INC.

                                  By: /s/ Ludger H. Viefhues
                                     ___________________________________________
                                     Ludger H. Viefhues, Chief Executive Officer



                                  /s/ Ralph D. Hartung
                                  ______________________________________________
                                  Ralph D. Hartung