This is an open-label, multi-center, long-term treatment study conducted only in Japanese sites. The subjects are patients who fulfill the diagnostic criteria for bipolar I disorder, most recent episode depressed, as defined in the Diagnostic and Statistical Manual of Mental Disorders Fourth Edition, Text Revision (DSM-IV-TR) (296.50=unspecified, 296.52=moderate severity, 296.53=severe without psychotic features, 296.54=severe with psychotic features), who have completed Study HGMP (NCT#00510146) and patients who did not participate in Study HGMP who have been recruited to participate in Study HGMS.