Bipolar disorder is rapidly becoming the primary diagnosis in adult psychiatry. It represents a wide spectrum of disorder all sharing common features of elated and depressed mood. The early descriptions of symptom-free euthymia have long been dismissed and the chronic and enduring deficits associated with the disorder are beginning to be better understood. The course of the disorder remains uncertain especially in light of the recently observed increases in children receiving the diagnosis. There is growing interest in the elated states seen as a common adolescent phenotype.There is a simplified view of the illness as an episodic course interspersed with euthymia, short-term treatments being used in acute episodes and long-term treatments being indefinite and intended to prevent new episodes. However, subsyndromes, co-morbidities and a variety of chronic symptoms are common in bipolar disorder. In practice, they often drive treatment decisions. Chronic symptoms are usually related to anxiety, depression or cognition and are a disabling aspect of the long-term outcome. Unfortunately, there is little to guide the selection of treatment to reduce the impact of these symptoms since they have almost never been the subject of clinical trials.The use of medication in combinations is the usual practice in bipolar disorder. The argument to favour this in guidelines is highly pragmatic, but there is a growing evidence base to support it. Lithium remains a key benchmark treatment for comparing alternatives in long term efficacy. Its effects against suicide are particularly important.