The purpose of this study is to assess olanzapine/fluoxetine combination and lamotrigine comparative efficacy, safety and tolerability in acute and longer term treatment of bipolar depression.

Inclusion Criteria:

• Male or female patients, 18 to 60 years of ages, inpatients or outpatients. Inpatients are qualified only if they are hospitalized for current episode of bipolar depression and should be able to leave hospital when clinical criteria are no longer met for acute inpatient hospitalization
• Patients must fulfill the criteria for bipolar I depression (bipolar I disorder, current episode major depressive) as defined in DSM-IV-TR based on clinical examination and psychiatric assessment
• Patients must have experienced, in the opinion of the investigator, at least one previous manic or mixed episode as defined in DSM-IV-TR, of sufficient severity to require treatment with a mood stabilizer or an antipsychotic as reported by the patient or the caregiver
• Each patient must have a level of understanding sufficient to perform all tests and examinations required by the protocol
• Female patients must test negative for pregnancy and must be using a medically accepted means of contraception

Exclusion Criteria:

• Current diagnosis of any of the following according to DSM-IV-TR criteria: Schizophrenia, Schizophreniform Disorder, Schizoaffective Disorder, Delusional Disorder, Delirium of any type, Dementia of any type, Amnestic Disorder, any Substance-Induced Disorder, or any Psychotic Disorder due to a General Medical Condition, unless there is substantive reason to believe patient was previously misdiagnosed.
• Treatment with clozapine within 3 months (90 days) prior to visit 1
• Treatment with electroconvulsive therapy (ECT) within 3 months (90 days) prior to visit 2
• Patients with seizure disorders are excluded (except patients with a previous history of seizures due to alcohol withdrawal, which have resolved).
• Participation in a clinical trial of another drug including olanzapine, fluoxetine or lamotrigine within 30 days prior to study entry (visit 1)