Over the last 20 years there has been increasing recognition that bipolar disorder is often a very severe and potentially disabling psychiatric condition. This has been accompanied by an increase in research into many aspects, ranging from molecular genetics to treatment and outcome. The boundary between unipolar and bipolar affective disorder has become less clear than we once thought, as milder and sub-threshold bipolar forms have become recognised. The range of available treatments has expanded, with recognition of mood-stabilising effects of some antiepileptic drugs, and application of psychological approaches such as cognitive therapy and psychoeducation. The specific indications and best places in practice of some of the newer treatments are still in the process of becoming well defined. In the UK, as mental health specialist services have become focussed on severe disorders, patients with bipolar disorder have become important in clinical management for all members of the mental health team.