Researchers at the Psychotic Disorders Research Program in the Department of Psychiatry at UMass are looking for volunteers for an NIH-funded research study involving schizophrenia and marijuana use. We are studying whether an FDA-approved drug, clozapine, can reduce marijuana use in individuals who suffer from schizophrenia and ongoing marijuana use. Eligibility: people age 18-55 who suffer from schizophrenia or schizoaffective disorder; and meet the criteria for marijuana abuse or dependence. Exclusion criteria include: people who suffer from any substance abuse disorder other than caffeine, nicotine, and alcohol abuse disorder or who currently receive treatment with clozapine or risperidone or suffer from a medical condition in which treatment with clozapine or risperidone would be impractical or unsafe. People in the study will be compensated for their time. All information is kept private. If you are interested and would like more information, please call Radhika Natarajan at 508-856-8323 or email: Radhika.Natarajan@umassmed.edu.