The purpose of the study is to evaluate the efficacy of quetiapine compared to valproate during a 12 month treatment period in subjects with Bipolar Disorder I or II with Rapid Cycling.

Inclusion Criteria:

• Signed informed consent, men and women aged ³18 to £65 years with diagnosis of DSM-IV criteria for bipolar I or II disorder, most recent episode manic, hypomanic, mixed or depressive with Rapid Cycling.

Exclusion Criteria:

• Substance or alcohol dependence, female patients who are pregnant, lactating or at risk of pregnancy, diagnosis of schizophrenia or borderline personality disorder or antisocial personality disorder, history of seizure disorder, acute suicidal or external aggressive behaviour, legal incapacity or indication for treatment against the will of the patient by law.