Bipolar disorder, a brain disorder that causes unusual shifts in a person's mood, affects approximately one percent of the population. It commonly occurs in late adolescence and is often unrecognized. The diagnosis of bipolar disorder is made on the basis of symptoms, course of illness, and when possible, family history. Thoughts of suicide are common with this disorder. Included are descriptions of the signs of the manic episodes and the depressive episodes. The classic form the illness is called bipolar I disorder and involves recurrent episodes of mania and depression. Milder episodes of mania that alternate with depression are called bipolar II disorder. There is no single cause of this illness but rather a combination of factors produce the illness. Genetics play a role but are not the sole contributing factor. Children can develop this disorder and it is often hard to tell it apart from other disorders that affect this age group. People with bipolar disorders can lead healthy and productive lives when the illness is effectively treated. A combination of medication and psychosocial treatment is optimal for managing the disorder over time. A list of national organizations is included for further information. (Contains 26 references.) (JDM)