Manic depression, or bipolar disorder, is a multifaceted illness with an inevitably complex treatment. The current article summarizes the current status of our knowledge and practice concerning its diagnosis and treatment. While the prototypic clinical picture concerns the "classic" bipolar disorder, today mixed episodes with incomplete recovery and significant psychosocial impairment are more frequent. The clinical picture of these mixed episodes is variable, eludes contemporary classification systems, and possibly includes a constellation of mental syndromes currently classified elsewhere. Treatment includes the careful combination of lithium, antiepileptics, atypical antipsychotics, and antidepressants, but not all of the agents in these broad categories are effective for the treatment of bipolar disorder.