This trial will consist of 1600 patients with schizophrenia for whom a medication change may be indicated for reasons of limited efficacy or tolerability. All patients will receive some psychosocial treatment through study participation. Research participants and their family members will be offered psychosocial interventions directed at improving patient and family understanding of the illness, decreasing the burden of illness in the family, maximizing treatment adherence, minimizing relapse, enhancing access to a range of community-based rehabilitative services and improving study retention.

Phase I: Patients will be randomly assigned to one of five treatment conditions for up to 18 months:

1. 320 begin double-blind treatment with perphenazine (PER)
2. 320 begin double-blind treatment with olanzapine (OLZ)
3. 320 begin double-blind treatment with quetiapine (QUET)
4. 320 begin double-blind treatment with risperidone (RIS)
5. 220 begin double-blind treatment with ziprasidone (ZIP)

Phase IA: 100 patients screened and found to have tardive dyskinesia who would otherwise be eligible for the study will be randomly assigned to one of the four atypical drugs in Phase IA.

Phase IB: Patients who fail treatment with perphenazine in Phase I will be randomly assigned to olanzapine, quetiapine, or risperidone in Phase IB.

Phase II: Patients who discontinue their initial assigned atypical antipsychotic treatment in Phase I, IA, or IB for any non-administrative reason will proceed to their second assigned treatment (third for Phase IB patients) and will be followed for up to the remainder of their 18-month participation, as follows:

1. Patients originally assigned to one of the newer atypical antipsychotics who discontinue due to efficacy failure will be randomly assigned to double-blind treatment with one of the other two newer atypical antipsychotics (OLZ, RIS, QUET) which they had not previously received (50%) or with open label clozapine (50%).
2. Patients originally assigned to one of the newer atypical antipsychotics who discontinue due to tolerability failure will be randomly assigned to double-blind treatment with one of the other newer atypical antipsychotics (OLZ, RIS, QUET) which they had not previously received (50%), or with ziprasidone (50%). Until ziprasidone is activated, all patients will be assigned to one of the other atypical antipsychotics.

Phase II will last at least 6 months, even if that means participants stay in the study for more than 18 months

Phase III: Patients who discontinue Phase II will be recommended open treatment with the preferred regimen based on their treatment history in the study. The treatment options include clozapine, newer atypical antipsychotic (olanzapine, risperidone, quetiapine, ziprazidone, and aripiprazole), fluphenazine decanoate, perphenazine, and dual antipsychotic therapy using two of these drugs.

Note: All treatments will be double-blinded in treatment Phases I and II except for clozapine.