Through a review of randomised, controlled trials, this article evaluates the efficacy and tolerability of quetiapine in the acute and maintenance phases of bipolar disorder. In trials involving mania patients, quetiapine was found to be effective as adjunctive therapy in combination with lithium or valproate, significantly superior to placebo, and equal to lithium or haloperidol as monotherapy. With regard to the prevention of relapses in bipolar disorder, quetiapine seems to differ from other atypical antipsychotics in its characteristics as a mood stabiliser, which are associated with a promising efficacy in the treatment of bipolar depressive episodes. However, further larger controlled long-term prospective studies are needed to confirm the efficacy of quetiapine for the prevention of relapses in bipolar disorder. Quetiapine seems to have a satisfactory safety and tolerability profile, with a low prevalence of extrapyramidal symptom-related adverse events, treatment-emergent depression and weight gain. Sedation is the main side effect of treatment with quetiapine.