The authors report the results of a before-and-after evaluation of an on-site mental health day treatment program for homeless men. Thirty-two subjects were interviewed 6 or more months after placement from a crisis shelter to community housing in order to probe housing stability, aftercare treatment compliance, employment, rehospitalization, and criminal justice contacts. In the after phase, living on the street was virtually eliminated, use of shelters decreased sevenfold, aftercare utilization tripled, and contacts with the criminal justice system were halved. Psychiatric hospitalizations and unemployment were higher in the after phase. Findings are discussed in relation to the need to conduct controlled experiments of new psychosocial treatments for the homeless mentally ill.