Toronto Mayor Rob Ford has acknowledged a drug problem for the first time and vowed his commitment to "living clean is now unwavering" as he returned to work after a two-month stay in rehab.
Ford read an emotional statement at City Hall, but refused to take questions, after checking out of a facility in Ontario.
The mayor of Canada's largest city said staff at the rehab facility saved his life.
"For a long, long time I resisted the idea of getting help," he said. "Like a lot of people dealing with substance abuse, I was in complete denial. But it soon became obvious that my alcohol and drug use was having a serious, serious impact on my family, on my health and on my job as mayor."
Ford didn't specify which drug or drugs, but he acknowledged last year that he had smoked crack in a "drunken stupor".
Ford said the road to recovery remains long. He called addiction a chronic medical condition but said he looks forward to serving the residents of Toronto for many more years.
"When I look back at some of the things I said and some of the things I did when I was using, I'm ashamed, I'm embarrassed, I'm humiliated," he said.
Ford has not abandoned his effort to seek a second term in October. Toronto's City Council stripped Ford of most of his powers last year.
He announced in late April that he would seek help for alcohol addiction. He made the decision after a video surfaced that apparently showed him smoking crack cocaine.
Reports last year of a similar video led to months of denials before Ford made his statement about smoking crack in a "drunken stupor".
His decision to seek treatment came months after he announced he was finished with alcohol - only to be followed by a steady flow of reports of intoxicated behaviour.
Many councillors expressed reservations about his return.
"He's put Toronto on the map worldwide for reasons that none of us would want," Councillor John Parker said.
Doug Ford, Ford's brother and a city councillor, has said Rob Ford will resume campaigning right away. He said his brother loves being mayor and is fighting for his political life.