This is a randomized, parallel, open-label study of patients who have responded to treatment in the acute phase of their manic or mixed episode, with or without psychotic symptoms, with olanzapine in mono or co-therapy, and who are in syndromic and symptomatic remission at the time of enrollment into the study.

Inclusion Criteria:

• Outpatients, male or female, at least 18 years old
• Patient or legal representative must understand the study and sign an informed consent document before any study procedure
• Must have a diagnosis of Bipolar Disorder type I and have a recent manic or mixed episode, with or without hospitalization, according to DSM-IV-TR criteria.
• Patients must be in syndromic and symptomatic remission, following DSM-IV-IR criteria, for the manic or mixed episode, at the time of study entry, with a total score for YMRS less than or equal to 12 and total store for HAMD less than or equal to 8 at visit 1 and 2.
• Remission must have been achieved taking olanzapine in mono or co-therapy, and it must have been maintained until study entry.
• Patients must have had, at least, 2 manic or mixed episodes within 3 years of the study entry, taking into account the current one.

Exclusion Criteria:

• Have received treatment within the last 30 days with a drug that has not received regulatory approval for any indication at the time of study entry, or with a study drug in other clinical trial
• Patients without symptoms or manic or mixed episode within one month of study entry.
• Confirmed diagnoses of Schizophrenia or other psychotic disorders (schizophreniform disorder, schizoaffective disorder, delusional disorder, brief psychotic disorder, shared psychotic disorder, substance-induced or medical condition psychotic disorder, psychotic disorder NOS),following DSM-IV-TR criteria.
• Patients that have achieved remission with ECT (electro convulsive therapy) in addition to psychopharmacological treatment
• Drug dependence or abuse, if it is a primary diagnose and the mood disorder is due to his administration
• Patients that at the time of study entry or at any other time of study, need treatment with antiepileptics or other substances with potential effect as mood stabilizers (i,e new antiepileptics different to Lithium, Valproic Acid and/or Carbamazepine