EXHIBIT 10.1

                        CITADEL INVESTMENT GROUP, INC.
                    225 West Washington Street, Ninth Floor
                            Chicago, Illinois 60606

                              September 24, 1996

Mr. Marc W. Eller
SI Diamond Technology, Inc.
12100 Technology Blvd.
Austin, Texas 78727

      Re: Holdback and Other Agreements Relating to Series E Preferred Stock

      Reference is made to the Statement of Designations, Preferences and Rights
of Series E Preferred Stock of SI Diamond Technology, Inc. filed with the Office
of the Secretary of State of Texas on January 4, 1996 (the "Designation"). 
Capitalized terms used but not defined herein have the respective meanings set 
forth in the Designation.

      In order to accommodate the Corporation's attempt to acquire additional 
financing and subject to your acceptance of this letter (as indicated by your 
execution and delivery of a signed counterpart hereof to each of the 
undersigned), the undersigned holders of the Series E Preferred Stock agree to 
take the following actions on the following terms subject to the conditions set 
forth herein.

      1. Conversion. During the period beginning on or after September 16, 1996,
and ending on or prior to the date of your acceptance of this letter, the 
Holders of Series E Preferred Stock shall convert shares of Series E Preferred 
Stock (the "Mandatory Conversion Amount") into an aggregate of approximately 
300,000 shares of Common Stock at the Conversion Rate in effect on September 16,
1996. Unless otherwise agreed to by the Holders of Series E Preferred Stock, the
conversions contemplated by this paragraph 1 shall be made by the Holders pro 
rata based on the number of shares of Series E Preferred Stock originally 
issued to each such Holder.

      2. Holdback. Each Holder of Series E Preferred Stock agrees not to convert
any shares of Series E Preferred Stock into Common Stock pursuant to Section 5 
of the Designation during the period from the date of acceptance of this letter 
to and including October 31, 1996 (the "Financing Period"). In addition, if and 
only if (a) the Corporation has raised $1,000,000.00 in net proceeds from its 
issuance of debt and/or equity during the Financing Period, (b) such proceeds 
are available to the Corporation for general working capital purposes prior to 
the expiration of the Financing Period and (c) the Corporation has delivered to 
each of the Holders of Series E Preferred Stock a certificate of the chief 
financial officer of the Corporation certifying the receipt and availability of 
such proceeds prior to the expiration of the Financing Period, each Holder of 
Series E Preferred Stock agrees (x) not to convert any shares of Series E 
Preferred Stock into Common Stock during the period from and including November 
1, 1996 to and including January 14, 1997, and (y) not to convert shares of 
Series E Preferred Stock in excess of the Agreed Convertible Amount into Common 
Stock during the period from and including January 15, 1997 to and including 
February 28, 1997. For purposes of this paragraph 2, the "Agreed Convertible 
Amount" shall mean, with respect to any Holder of Series E Preferred Stock, an 
amount of shares of the Series E Preferred Stock equal to one-third of the 
shares of Series E Preferred Stock held of record by such Holder as of the start
of the trading day on September 16, 1996, less the number of shares of Series E 
Preferred Stock converted into Common Stock by such Holder during the period 
from and including September 16, 1996 to and including the date of the 
acceptance of this letter pursuant to paragraph 1.


 
Mr. Marc W. Eller
September 24, 1996
Page 2

       3. Consideration for Holdback. In consideration for the agreements of
  each of the Holders of Series E Preferred Stock set forth in paragraph 2
  above, the Corporation agrees that the Fixed Conversion Price shall be reduced
  from $6.575 to $3.00. The Corporation hereby agrees to take all necessary and
  desirable action, including without limitation the preparation of definitive
  documentation evidencing such agreement and/or the amendment of the
  Designation, to give legal and binding effect to the agreement referred to in
  the preceding sentence on or prior to September 27, 1996, or, in the event
  that this letter is not executed by the number of Holders of Series E
  Preferred Stock required under law to effect an amendment to the Designation,
  as soon thereafter as practicable. Each of the Holders of Series E Preferred
  Stock hereby agrees that this letter constitutes such Holder's written consent
  to amend the Designation as provided in the first sentence of this paragraph 3
  as required by Section 9 of the Designation.

       4. Condition to Holdback. The obligation of each Holder of the Series E
  Preferred Stock set forth in paragraph 2 above shall cease and be of no
  further force or effect at any time after (a) the average Closing Bid Price of
  the Corporation's Common Stock for five consecutive trading days exceeds $3.00
  or (b) Marc W. Eller ceases to be employed by the Corporation in substantially
  the same capacity as he occupies as of the date hereof.


   If you are in agreement with the foregoing terms and conditions, please 
execute a counterpart to this letter in the space below and return a copy by 
facsimile with hard copy to follow by overnight courier to each of the 
undersigned Holders of Series E Preferred Stock at the address set forth on the 
books and records of the Corporation prior to 5:00 p.m. EDT, September 25, 1996.


                                Sincerely,


OLYMPUS SECURITIES, LTD.                     NELSON PARTNERS                 
                                                                             
                                                                             
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Name:                                        Name:                           
Title:                                       Title:                          

LEONARDO, L.P.                               GRACECHURCH & CO.              
                                                                            
                                                                            
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Name:                                        Name:                          
Title:                                       Title:                          


RAPHAEL L.P.                                 AG SUPERFUND INT'L             
                                                                            
                                                                            
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Name:                                        Name:                          
Title:                                       Title:                          


WEST MERCHANT BANK NOMINEES LTD              GAM L.P.
                                                                            
                                                                            
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Name:                                        Name:                          
Title:                                       Title:                          



 
Mr. Marc W. Eller
September 24, 1996
Page 3


    The undersigned Holders of Series E Preferred Stock are executing this 
letter solely for the purpose of consenting to the amendment of the Designation 
as provided in the first sentence of paragraph 3 as required by Section 9 of the
Designation.


LA ROCQUE TRADING GROUP LLC                  KA TRADING L.P.                
                                                                            
                                                                            
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Name:                                        Name:                          
Title:                                       Title:                          



Accepted and agreed
as of September 25, 1996:



SI DIAMOND TECHNOLOGY, INC.           
                                      
                                      
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       Marc W. Eller