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. In addition, transitioning to a different antipsychotic drug is at times a necessary step in the clinical management of patients with schizophrenia due to different reasons, including insufficient response and poor tolerability. This is an open-label, non-randomized study of a formulation of risperidone (RISPERDAL® CONSTA™) (coated microspheres) injected into the muscle at week intervals over 6 months in patients with schizophrenia or schizoaffective disorder. During the first 3 weeks, oral olanzapine treatment is continued to provide therapy until the risperidone long-acting injectable reaches effective drug levels. The oral olanzapine treatment is tapered off within 1 week for one group of patients and within 3 weeks for another group. Assessments of effectiveness include the Positive and Negative Syndrome Scale (PANSS), overall severity of illness measured by the Clinical Global Impression (CGI) scale, and quality of life evaluated by the SF-36 questionnaire. Safety evaluations include incidence of adverse events through out the study and Extrapyramidal Symptom Rating Scale (ESRS), clinical laboratory tests (biochemistry, hematology, and urinalysis), and physical exams, including body weight, at specified intervals. The study hypothesis is that changing to treatment every 2 weeks with long-acting risperidone will provide a maintained effectiveness patients with schizophrenia or schizoaffective disorder and will be generally well-tolerated Risperidone, long-acting formulation for intramuscular injection (25 milligrams[mg]) every 2 weeks for 6 months. Investigator may adjust dosage to 37.5mg or 50mg (maximum) or supplement risperidone injections with risperidone tablets (2mg maximum), according to symptoms and treatment response.