"This is the right time for both Mr. Duperreault and Mr. Greenberg," ACE spokesperson Anna Lowry told National Underwriter. "Mr. Duperreault was looking to reduce his responsibilities."

Once seen as a potential successor to his father, American International Group Inc. Chairman and CEO Maurice Greenberg, Evan Greenberg, 49, moved to take a senior position at ACE in November 2001 to lead its worldwide reinsurance business.

Mr. Duperreault commented that Evan Greenberg "distinguished himself very quickly" when he assumed the leadership of ACE's global reinsurance business in November 2001 and brought record profitability to that operation.

"Evan has done an outstanding job running ACE on a day-to-day basis as its chief operating officer since June of 2003. He is the right person to lead ACE in the next generation," Mr. Duperreault said.

ACE Ltd. sells property-casualty insurance and reinsurance in the United States and about 50 other countries through its subsidiaries. For full-year 2003, the company's net income was a record $1.4 billion, improving from $77 million in profit for the prior year.

"I have very good feelings?it's the right thing to do for everyone," Mr. Duperreault told analysts during a conference call this afternoon. He also added that Mr. Greenberg has "earned the right to take over as the CEO."

"Evan will do a fabulous job. I had this job for 10 years?10 years of remarkable growth and development. Now a new CEO comes in with a fresh approach, new ideas, energy, focus?so I think this is good for the company," he said.

Mr. Duperreault said he will continue to work on governmental affairs. "I've spent a lot of time in Washington working with others on reforms like asbestos and class action. I expect to continue to do that."

Commenting on his new chief executive post, Mr. Greenberg told analysts he was "downright excited."

"What a fabulous opportunity," he said. "I am grateful for the responsibility that's been entrusted to me. I couldn't be more optimistic about the future and the tremendous platform we have to build from."