Bipolar disorder is a complex mental illness that is frequently both under-diagnosed and under-treated. The symptoms of bipolar disorder can be confused with other medical illnesses or drug effects or may even be overlooked entirely as extreme character traits. The consequences of delayed diagnosis or misdiagnosis are potentially devastating, including loss of employment, impaired relationships and a severely impaired quality of life. This article will review the historic perspectives of bipolar disorder, the diagnostic criteria for the phases of the illness, and the pharmacologic options available to treat this condition. Quetiapine, an atypical antipsychotic, will be reviewed indepth. Based on extensive trial data, reviewed in this article, quetiapine is approved by the US Food and Drug Administration for use as monotherapy or as adjunctive therapy with other mood stabilizers for the treatment of acute manic episodes of bipolar I disorder. Clinical trials describing the efficacy of quetiapine in other phases of bipolar disorder and in other patient populations are also reviewed. A discussion of the drug profile of quetiapine includes its chemistry, availability, pharmacodynamics, pharmacokinetics and metabolism. Preclinical studies, postmarketing surveillance, safety, tolerability and regulatory issues are also evaluated. Finally, potential future directions for quetiapine are discussed, together with a review of key issues in bipolar disorder management and details of the information resources used in preparing this article.