**Exhibit **31.1****

**CERTIFICATION PURSUANT TO RULE 13a-14(a) OF THEEXCHANGE ACT, AS ADOPTED PURSUANT TO SECTION 302 OF THE SARBANES-OXLEY ACTOF 2002**

I, Robert K. Weiler,certify that:

*1.**               *I have reviewed this QuarterlyReport on Form 10-Q of Phase Forward Incorporated;

*2.**               *Based on my knowledge, this reportdoes not contain any untrue statement of a material fact or omit to state amaterial fact necessary to make the statements made, in light of thecircumstances under which such statements were made, not misleading withrespect to the period covered by this report;

*3.**               *Based on my knowledge, thefinancial statements, and other financial information included in this report,fairly present in all material respects the financial condition, results ofoperations and cash flows of the registrant as of, and for, the periodspresented in this report;

*4.**               *The registrant’s other certifyingofficer(s) and I are responsible for establishing and maintainingdisclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and15d-15(e)) for the registrant and have:

*(a)*   Designed such disclosure controls andprocedures, or caused such disclosure controls and procedures to be designedunder our supervision, to ensure that material information relating to theregistrant, including its consolidated subsidiaries, is made known to us byothers within those entities, particularly during the period in which thisreport is being prepared;

*(b)*   [Paragraph omitted in accordance with SECtransition instructions contained in SEC Release 34-47986.]

*(c)*    Evaluated the effectiveness of theregistrant’s disclosure controls and procedures and presented in this reportour conclusions about the effectiveness of the disclosure controls andprocedures, as of the end of the period covered by this report based on suchevaluation; and

*(d)*   Disclosed in this report any change in theregistrant’s internal control over financial reporting that occurred during theregistrant’s most recent fiscal quarter (the registrant’s fourth fiscal quarterin the case of an annual report) that has materially affected, or is reasonablylikely to materially affect, the registrant’s internal control over financialreporting; and

*5.**               *The registrant’s other certifyingofficer(s) and I have disclosed, based on our most recent evaluation ofinternal control over financial reporting, to the registrant’s auditors and theaudit committee of the registrant’s board of directors (or persons performingthe equivalent functions):

*(a)*   All significant deficiencies and materialweaknesses in the design or operation of internal control over financialreporting which are reasonably likely to adversely affect the registrant’sability to record, process, summarize and report financial information; and

*(b)*   Any fraud, whether or not material, thatinvolves management or other employees who have a significant role in theregistrant’s internal control over financial reporting.

Date:      August 10,2005
| By:      |     | /s/ ROBERT K.  WEILER     |
|----------|----------|---------------------------|
|     |     | Robert K. Weiler          |
| * * | * * | *Chief Executive Officer* |

 

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