Immediate Release (IR) to Sustained Release (SR) Switching Study: Study of Switching From IR Seroquel to SR Seroquel in Outpatients With Schizophrenia

Inclusion Criteria: * A stable dose of quetiapine IR between 300 and 800 mg/day within 4 weeks prior to the enrolment visit (Visit 1) as judged by the investigator. * Female patients of childbearing potential must have a negative serum pregnancy test at enrolment and be willing to use a reliable method of birth control, ie, barrier method, oral contraceptive, implant, dermal contraception, long-term injectable contraceptive, intrauterine device, or tubal ligation during the study. * Able to understand and comply with the requirements of the study, as judged by the investigator. Exclusion Criteria: * Meeting the criteria for any other (than schizophrenia) Diagnostic and Statistical Manual of Mental Disorders, 4th Edition (DSM-IV) Axis I diagnosis, concomitant organic mental disorder or mental retardation. * Patients with substance abuse or dependence, as defined by DSM-IV, and not in full remission. A urine drug screen test will be performed. The investigator will evaluate the results along with medical history to determine if the patient meets DSM-IV criteria for substance abuse or dependence. * Risk of transmitting human immunodeficiency virus (HIV) or hepatitis B, via blood or other body fluids, as judged by the investigator. * Patients who, in the opinion of the investigator, pose an imminent risk of suicide or a danger to self or others.