This article presents an overview of bipolar disorder (BPD) in children, a condition that only recently has been recognized as a legitimate diagnosis. Bipolar disorder in children is underrecognized for many reasons including lack of awareness, diagnostic confusion, and the different clinical picture in children. Available data strongly suggest that prepubertal childhood BPD is a non-episodic, chronic, rapid cycling, mixed manic state. It may be comorbid with attention-deficit/hyperactivity disorder (ADHD) and conduct disorder (CD) or it may demonstrate features of ADHD and CD, further complicating recognition and subsequent treatment. Treatment issues are discussed, and some reasons for the urgency of early recognition and treatment are explained.