Last July, Gil Scott-Heron, the musician, poet and activist, promised a judge that he would enter a residential drug treatment program in September, as soon as he returned from a summertime tour of Europe. It was his last chance to avoid prison for his felony conviction for possession of cocaine.

He returned but did not keep his promise. By the last week of October, he had made no effort to get into treatment, prosecutors said, so Justice Carol Berkman of State Supreme Court in Manhattan sentenced him to one to three years in prison.

Mr. Scott-Heron said little at his court appearance. He has always denied that he has a drug problem, but friends and associates have concluded that he has been addicted to cocaine, and particularly crack cocaine, for years. Justice Berkman agreed.

At 52, Mr. Scott-Heron has lost many of his teeth, appears emaciated and sometimes slurs his speech.

There was always a question whether any rehabilitation program would work for someone like him, someone who did not want to participate and did not acknowledge a problem.