This study is an open, randomized, controlled study to compare intramuscular long-acting risperidone to oral risperidone with blinded ratings to determine whether the long-acting form of risperidone has greater efficacy in reducing substance use. Patients with schizophrenia or schizoaffective disorder, age 18 to 65, who are taking any single oral antipsychotic medication except clozapine or risperidone long-acting may be enrolled.