Derrick Williams' work sells, but he doesn't paint for the money.

"As long as I'm able to [paint], I'll do it," says Mr. Williams, who has had several exhibitions recently through his affiliation with the Fountain Gallery in New York City. "I feel that this is a calling."

Mr. Williams, 37, lives in the Bronx, and is a member of Fountain House and the Fordham Tremont Continuing Care Clinic. He got his start in the art world by taking first place in a poster contest sponsored by the clinic.

Raised by his grandmother, he was labeled as emotionally disturbed when he was a child. His current diagnosis is schizoaffective disorder.

Growing up, Mr. Williams studied ...