A Study of Relapse Prevention and the Effectiveness of Long-acting Injectable Risperidone and Quetiapine Tablets in the Treatment of Patients With Schizophrenia or Schizoaffective Disorder

- Diagnosis of schizophrenia or schizoaffective disorder according to the Diagnostic and Statistical Manual of Mental Diseases, 4th edition (DSM-IV)

- Patients currently treated with oral risperidone, olanzapine or a conventional neuroleptic monotherapy at doses not exceeding 6 mg risperdal, 20 mg olanzapine, or a conversion dose of 10 mg haloperidol for oral conventional agents

- Patients who are stable (judged clinically stable by the investigator and on a stable dose of medication for 4 weeks or longer) but not optimally treated (non-satisfactory treatment regarding symptoms or adverse events)

- Diagnosis other than schizophrenia or schizoaffective disorder by DSM-IV Axis I criteria

- Patients being treated with antipsychotic agents other than oral risperidone, olanzapine or conventional oral neuroleptic agents

- Patients with known hypersensitivity to oral risperidone, quetiapine, aripiprazole, or who are known non-responders to oral risperidone, quetiapine, aripiprazole or to previous treatment with at least 2 antipsychotic agents

- Patients treated with mood stabilizers or antidepressants who are not on stable dose for at least 3 months before study initiation

- Pregnant or nursing females, or those lacking adequate contraception