ASPEN TECHNOLOGY INC /DE/
EXHIBIT 10.6
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<DESCRIPTION>EXHIBIT 10.6
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<P ALIGN="RIGHT"><FONT SIZE=2><B>Exhibit 10.6  </B></FONT></P>

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<TD WIDTH="8%"><FONT SIZE=1>&nbsp;</FONT></TD>
<TD WIDTH="3%"><FONT SIZE=1>&nbsp;</FONT></TD>
<TD WIDTH="28%"><FONT SIZE=1><B>Aspen Technology,&nbsp;Inc. Ten Canal Park</B></FONT></TD>
<TD WIDTH="3%"><FONT SIZE=1>&nbsp;</FONT></TD>
<TD WIDTH="28%"><FONT SIZE=1><B>[phone]</B></FONT><FONT SIZE=1> 617 949 1000</FONT></TD>
<TD WIDTH="3%"><FONT SIZE=1>&nbsp;</FONT></TD>
<TD WIDTH="28%"><FONT SIZE=1><B>[world wide web]</B></FONT><FONT SIZE=1> www.aspentech.com</FONT></TD>
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<TD WIDTH="8%"><FONT SIZE=1>&nbsp;</FONT></TD>
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<TD WIDTH="28%"><FONT SIZE=1>Cambridge MA 02141-2201 USA</FONT></TD>
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<TD WIDTH="28%"><FONT SIZE=1><B>[fax]</B></FONT><FONT SIZE=1> 617 949 1030</FONT></TD>
<TD WIDTH="3%"><FONT SIZE=1>&nbsp;</FONT></TD>
<TD WIDTH="28%"><FONT SIZE=1><B>[e-mail]</B></FONT><FONT SIZE=1> info@aspentech.com</FONT></TD>
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<P><FONT SIZE=2>[ASPENTECH LOGO] </FONT></P>

<P><FONT SIZE=2>June&nbsp;24,
2003 </FONT></P>

<P><FONT SIZE=2>Mr.&nbsp;Steve
Pringle<BR>
Senior VP Manufacturing/Supply Chain Product Business Unit (PBU) </FONT></P>

<P><FONT SIZE=2>Dear
Steve: </FONT></P>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;I
am pleased to confirm that the Compensation Committee of the AspenTech Board of Directors has approved the following FY04 Executive Compensation Plan for you. This Plan is contingent
upon shareholder approval of the Advent financing transaction, which is currently scheduled for August&nbsp;2003. </FONT></P>


<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Your
total target compensation for FY04 will be $334,000, which is comprised of a base salary of $230,000 and a bonus target of 45%. The actual bonus you earn will be determined by your
achievement of FY04 goals. I will communicate the details of the FY04 bonus program to you in early Q1 once the program has been finalized and approved by the Compensation Committee. </FONT></P>

<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;In
addition, you will be granted options to purchase 272,200 shares of AspenTech common stock at the Fair Market Value on the day the Advent transaction is approved by shareholders. This
grant, together with your existing option holdings, would bring your total equity participation level to approximately 0.400%, based on options with grant prices of $10/share or lower on a
pre-reverse split basis. In consideration for this substantial new grant, the following conditions apply, contingent upon closing of the Advent transaction and issuance of the options: </FONT></P>

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<DT style='margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD><FONT SIZE=2>For
your existing stock options with pre-split grant prices of $10/share or lower, you agree to only exercise these options in accordance with their normal
vesting schedule. In the event of your involuntary termination, or a change of control event as redefined in the 2001/2003 stock option plan and described in the proxy statement for the Advent
transaction, this restriction will be lifted.
<BR><BR></FONT></DD><DT style='margin-bottom:-11pt;'><FONT SIZE=2>&#149;</FONT></DT><DD><FONT SIZE=2>Your
existing employment/Change of Control agreement will be cancelled, and you will thereafter be entitled to receive, in the event your employment is terminated other than
for cause prior to June&nbsp;24, 2006, severance in an amount equal to your annual base salary then in effect, payable over 12&nbsp;months in accordance with AspenTech's semi-monthly payroll
schedule. </FONT></DD></DL>
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<P><FONT SIZE=2>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Steve,
I look forward to our continued work together as we drive shareholder value. </FONT></P>

<P><FONT SIZE=2>Best
regards, </FONT></P>

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<TD WIDTH="32%"><FONT SIZE=2>/s/ David L. McQuillin</FONT><HR NOSHADE><FONT SIZE=2> David L. McQuillin<BR>
President and CEO<BR>
Aspen Technology,&nbsp;Inc.</FONT></TD>
<TD WIDTH="3%"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD WIDTH="32%"><FONT SIZE=2>/s/ Steve Pringle</FONT><HR NOSHADE><FONT SIZE=2> Steve Pringle<BR>
Senior VP Manufacturing/Supply Chain PBU<BR>
Aspen Technology,&nbsp;Inc.</FONT></TD>
<TD WIDTH="3%"><FONT SIZE=2>&nbsp;</FONT></TD>
<TD WIDTH="32%" ALIGN="CENTER"><FONT SIZE=2>June&nbsp;24, 2003</FONT><HR NOSHADE><FONT SIZE=2> Date</FONT></TD>
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