Bipolar disorder is ranked as the sixth most important worldwide cause of disability. Current treatment is based chiefly on lithium and/or anticonvulsants, of which sodium valproate is the most widely used. A significant minority of patients fail to respond fully to current treatments, particularly those with mixed mania and/or rapid cycling. Many patients are unable to tolerate the side-effects of current therapy in the long term, and adverse effects may contribute to the high rate of noncompliance observed in bipolar disorder. The shortcomings of current treatments are reflected in poor outcomes: two-thirds of patients with bipolar disorder require hospitalization on more than one occasion; employment and social functioning are significantly lower than in control groups; 93% of carers suffer at least moderate distress; and 25-50% of patients are believed to attempt suicide at least once. Bipolar disorder shares some features with schizophrenia, and several atypical antipsychotics have demonstrated efficacy in bipolar disorder. Quetiapine has a particularly favourable tolerability profile, with placebo-level extrapyramidal symptoms and prolactin levels across the entire dose range combined with a neutral effect on weight during long-term use, and may be a valuable treatment option in acute mania and bipolar disorder.