A US senator who underwent emergency brain surgery last year, raising doubts over Democratic control of the Senate, has made his first public appearance.
Senator Johnson and his wife have both suffered from cancer
Senator Tim Johnson, 60, of South Dakota, told cheering supporters: "I'm back." He is expected to return to work next week, aides said.
Mr Johnson, whose speech is slurred as a result of his illness, said he was working hard to recover fully.
His return to the Senate cements the Democrats' one-seat majority there.
Had Mr Johnson stood down, the Republican governor of South Dakota would have named a successor - likely to be a Republican - to serve until the next general election in 2008.
Mr Johnson has not officially announced whether or not he will run for re-election next year but has hinted that he might.
"My will to keep fighting for you has never been stronger," he told the crowds during his appearance in Sioux Falls, South Dakota, on Tuesday evening.
Making light of his illness, he also joked that he had "an unfair edge" over most of his colleagues because his mind currently worked faster than his mouth did.
"Washington would probably be a better place if more people took a moment to think before they spoke," he said.
Mr Johnson was admitted to George Washington University hospital on 13 December after experiencing what his office initially said was a possible stroke.
He underwent emergency surgery for a bleeding on the brain and has been convalescing since.
The senator had prostate cancer in 2004 but says he is now clear of the disease. His wife has also had cancer.