The purpose of this study is to document the clinical benefit of quetiapine (Seroquel) sustained release (SR) after switching from another ongoing antipsychotic treatment, regardless of the reason for the switch.

PLEASE NOTE: Seroquel SR and Seroquel XR refer to the same formulation. The SR designation was changed to XR after consultation with FDA.

Inclusion Criteria:

• Patients who in their own and/or in the Investigator's opinion, consider ongoing antipsychotic treatment inadequate, because of insufficient efficacy and/or tolerability.
• 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.
• 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.