The purpose of this study is to investigate whether a long-acting injectable formulation of risperidone provides better effectiveness over 2 years, as measured by the time to relapse, compared with quetiapine tablets in a routine psychiatric care setting. Aripiprazole will be investigated in a descriptive manner.

Although many schizophrenia patients currently take oral antipsychotic medications, it is estimated that up to 75% of them have difficulty adhering to the daily oral regimen. Long-acting injectable formulations may eliminate the need for daily medication and enhance patient compliance with the treatment regimen. This is an open-label (all people involved know the identity of the intervention), randomized (study drug assigned by chance) study of a formulation of risperidone (coated microspheres) injected into the muscle at 2 week intervals over 104 weeks in stable patients with schizophrenia or schizoaffective disorder, who are being treated with oral risperidone, olanzapine, or other conventional antipsychotic agents. A comparator group will receive tablets of quetiapine to be taken 2 or 3 times daily, depending on the optimal dosage. In countries where aripiprazole is available, aripiprazole was also included in a descriptive manner. Reasons for switching symptomatically stable patients from their current antipsychotic treatment include insufficient effectiveness of the medication on symptoms, adverse events, or a patient's request. The principal measure of effectiveness of the drug is the time to relapse. Assessments of effectiveness also include: Positive and Negative Syndrome Scale (PANSS), which measures the symptoms of schizophrenia; overall severity of illness measured by the Clinical Global Impression subscale (CGI-S); patient's condition measured by the Clinical Global Impression condition subscale (CGI-C); quality of life assessed by the SF-12 survey. Safety evaluations include incidence of adverse events, Extrapyramidal Symptoms Rating Scale (ESRS), clinical laboratory tests (biochemistry, haematology, and urinalysis), and vital signs (pulse, blood pressure). The study hypothesis is that treatment with long-acting risperidone injected intramuscularly every 2 weeks provides better effectiveness than quetiapine, as measured by time to relapse, in patients with schizophrenia or schizoaffective disorder. Risperidone injections 25mg biweekly for 104 weeks, increasing or decreasing (increments of 12.5mg) at investigator's discretion. Risperidone tablets (2mg daily for 2 days) for patients starting on risperidone. Quetiapine and Aripiprazole used according to package insert.

Inclusion Criteria:

• 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)

Exclusion Criteria:

• 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