The purpose of this study is to determine the safety and efficacy of sustained-release quetiapine fumarate (Seroquel®) in the treatment of patients with Acute Bipolar Depression for 8 weeks.

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:

• Provision of written informed consent
• Documented diagnosis of Bipolar 1 disorder or Bipolar 11 disorder
• Outpatient status at enrollment

Exclusion Criteria:

• Patients with >8 mood episodes during the past 12 years
• Use of prohibited medications
• Substance or alcohol abuse or dependence
• Current suicide risk or suicide attempt within last 6 months.