"After much thought and consultation with my family and staff, I have decided to close this chapter of my service to Vermont and not seek re-election in 2006," said at a news conference at a suburban Burlington hotel.
Jeffords, 70, has been adamant in saying he will seek re-election, but there have been increasing concerns voiced about his health in recent weeks. He has suffered from a bad back and neck for years and lately has seemed confused by some questions in several news interviews.
The health of Jeffords' wife, Liz, has also been a concern. She is battling cancer.
Jeffords' surprise decision will unleash a host of candidates to replace him in the predominantly Democratic state. U.S. Rep. Bernie Sanders, the state's only congressman and the only independent in the House, has said he would run if Jeffords did not. Like Jeffords, he votes with the Democrats. Vermont's other member of the Senate is Democrat Patrick Leahy.
Republicans Richard Tarrant, a business executive, and Gov. James Douglas also are possible contenders.