EXHIBIT 10.4.5
                                                                  --------------

                            FIFTH AMENDMENT TO LEASE

LESSOR:           ATHENAEUM PROPERTY LLC

LESSEE:           BITSTREAM INC.

DATE OF LEASE:    MARCH 17, 1992;
                  (First Amendment September 7, 1993;
                  Second Amendment July 14, 1994;
                  Third Amendment July 15, 1996;
                  Fourth Amendment March 3, 1997)

PREMISES:         ATHENAEUM HOUSE, 215 FIRST STREET,
                  CAMBRIDGE, MASSACHUSETTS

FOR GOOD AND VALUABLE CONSIDERATION, the receipt and sufficiency of which
are hereby acknowledged,  the lease between Athenaeum Property LLC as Lessor and
Bitstream  Inc., a Delaware  corporation,  as Lessee  dated March 17, 1992,  and
amended  on  September  7, 1993 and by  letter  agreement  on July 14,  1994 and
amended on July 15, 1996,  and on March 3, 1997, is hereby amended for the fifth
time effective April 1, 1997, as follows:

         1.       "EXPANDED  LEASED  PREMISES."  Effective  June  1,  1997  (the
                  "Effective  Date") and  pursuant to  Paragraph 5 of the Fourth
                  Amendment to Lease,  the Leased  Premises  shall be reduced by
                  2800 rentable square feet ("Reduced Leased Premises"), more or
                  less,  on the ground floor of the Building as shown on Exhibit
                  A hereto.  Lessee  agrees it is giving up the  Reduced  Leased
                  Premises  in its "as is"  condition,  except  that the Reduced
                  Leased Premises shall be delivered to Lessor in vacuumed clean
                  condition, free of debris and personal effects.

         2.       ADJUSTED RENT. The Base Rent for the Leased Premises shall be
                  decreased as of the  Effective  Date by  $28,000.00  per year,
                  calculated as 2,800 square feet at $10.00 per rentable  square
                  feet,  representing  the  Base  Rent  on  the  Reduced  Leased
                  Premises.

         3.       DECREASED RENT ADJUSTMENT.  As of the Effective Date, the Rent
                  Adjustment  percentage in Paragraph 5 shall be decreased  from
                  8.66 percent to 7.68 percent.

         4.       CONSTRUCTION;  INTERPRETATION.  To the extent  that this lease
                  amendment  conflicts with the existing  lease,  this amendment
                  shall control.  Both parties  acknowledge the lease remains in
                  full force and effect. Other than as stated in this amendment,
                  all other terms and conditions remain the same.












         EXECUTED as a sealed instrument this 15th day of April, 1997.

ATHENAEUM PROPERTY LLC



By  /s/ Allan R. Jones                    /s/ Barbara J. Soper
    -----------------------------         ----------------------------- 
         President                          Witness
         Athenaeum F.A. Inc.
         Managing Member



BITSTREAM INC.



By:  /s/ James D. Hart                    /s/ John F. Dervishian
    ----------------------------------    ----------------------------- 
         Vice President, Treasurer and      Witness
         Chief Financial Officer
         Duly Authorized




                                    EXHIBIT A

                                                       "REDUCED LEASED PREMESIS"


         A floor plan of consisting of 2,800  rentable  square feet on the lower
level of the property located at 215 First Street,  Cambridge,  Massachusetts is
set forth on this Exhibit.




THE ATHENAEUM HOUSE                                           Rev.
215 First Street, Cambridge               Lower Level         May 1, 1997