POWER OF ATTORNEYPOWER OF ATTORNEY
 
For Executing Forms 3, 4 and 5
 
 
            The undersigned hereby constitutes and appoints each of Shawn Hoyt, 
Janet Mesrobian and Robert V. Jahrling as his or her true and lawful 
attorneys-in-fact to:
 
1. execute for and on behalf of the undersigned Forms 3, 4 and 
5 relating to changes in the undersigned's beneficial ownership of securities of 
Pegasystems Inc. and any necessary amendments to such forms, in accordance with 
Section 16(a) of the Securities Exchange Act of 1934 (as amended, the "1934 
Act") and the rules thereunder, and
 
2. do and perform any and all acts for and on behalf of the 
undersigned which may be necessary or desirable to complete the execution of any 
such Forms 3, 4 or 5 and the timely filing of such forms with the Securities and 
Exchange Commission and any other governmental authority.
 
The undersigned hereby grants to such attorneys-in-fact full power and authority 
to do and perform every act necessary and proper in the exercise of any of the 
rights and powers herein granted, as fully as such attorneys-in-fact could do if 
personally present, with full power of substitution or revocation, hereby 
ratifying and confirming all that such attorneys-in-fact shall lawfully do or 
cause to be done by virtue of this Power of Attorney and the rights and powers 
herein granted.  The undersigned acknowledges that the foregoing 
attorneys-in-fact, in serving in such capacity at the request of the 
undersigned, are not assuming any of the undersigned's liabilities under Section 
16 of the 1934 Act.
 
This Power of Attorney shall replace any previous Powers of Attorney signed by 
the undersigned with respect to the matters covered above and shall remain in 
effect for so long as the undersigned is required to file reports under Section 
16(a) of the 1934 Act with respect to securities of Pegasystems Inc.
 
IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be 
executed as of the 30th day of May, 2006.
 
/s/ James Reilly
                                                                        
 James Reilly