Subjects will be randomized to drug treatment with ziprasidone, olanzapine or risperidone, such that 30 subjects will receive ziprasidone, and 30 will receive either risperidone or olanzapine. Patients who enter the study on risperidone or with a history of risperidone treatment within the past 6 months will be randomized to either ziprasidone or olanzapine. Patients entering on olanzapine or with a history of olanzapine treatment within the past 6 months will be randomized to either ziprasidone or risperidone. Patients on other medications, with no history of olanzapine, risperidone or ziprasidone treatment, will be will be randomized to any of the three drugs. Patients treated with ziprasidone, at any time in the past, will be excluded. The final groups will consist of 30 subjects receiving ziprasidone, and 30 subjects receiving risperidone or olanzapine depending on their treatment history. Target dose for ziprasidone will be 160 mg/d with this dosage achieved within two weeks of initiation of drug treatment. Target dose for olanzapine will be 20 mg/d with this dosage achieved within two weeks of initiation of drug treatment. Target dose for risperidone will be 4 mg/d with this dosage achieved within two weeks of initiation of drug treatment. Dosage will be fixed at the target dose for the remainder of the trial. Patients who cannot tolerate the target dose will continue in the study, if feasible, and maintained at a lower dose. Extra-pyramidal side effects, if any, will be treated with benztropine as needed. Concomitant medications will not be permitted.