Exhibit 31.1

Sarbanes - Oxley Section 302 Certification
| I, Thomas J. May, certify that: |
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| 1.                    | I have reviewed this quarterly report on Form 10-Q of NSTAR; |
| 2.                    | Based on my knowledge, this quarterly report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances under which such statements weremade, not misleading with respect to the period covered by this quarterly report; |
| 3.                    | Based on my knowledge, the financial statements, and other financial information included in this quarterly report, fairly present in all material respects the financial condition, results of operations and cash flows of NSTAR as of,and for, the periods presented in this quarterly report; |
| 4.                    | NSTAR's other certifying officer and I are responsible for establishing and maintaining disclosure controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e)) for NSTAR and we have: |
|                                 | a)   | designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision, to ensure that material information relating to NSTAR, including its consolidated subsidiaries, ismade known to us by others within those entities, particularly during the period in which this quarterly report is being prepared; |
|                                 | b)   | evaluated the effectiveness of NSTAR's disclosure controls and procedures and presented in this quarterly report our conclusions about the effectiveness of the disclosure controls and procedures, as of the end of the period covered bythis quarterly report, based on such evaluation; and |
|                                 | c)   | disclosed in this quarterly report any change in NSTAR’s internal control over financial reporting that occurred during the most recent fiscal quarter that has materially affected, or is reasonably likely to materially affect,NSTAR’s internal control over financial reporting. |
| 5.                    | NSTAR's other certifying officer and I have disclosed, based on our most recent evaluation of internal control over financial reporting, to NSTAR's auditors and the audit committee of NSTAR's board of trustees: |
|                                 | a)   | all significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect NSTAR's ability to record, process, summarize and reportfinancial information; and |
|                                 | b)   | any fraud, whether or not material, that involves management or other employees who have a significant role in NSTAR's internal control over financial reporting. |
| Date:  August 4, 2004                     |     By: | /s/ THOMAS J. MAY        |
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|                                                                                                                                                    |                             | Thomas J. May                                               |
|                                                                                                                                                    |                             | Chairman, President and                                     |
|                                                                                                                                                    |                             | Chief Executive Officer                                     |