The clinical records of 53 adolescent inpatients diagnosed with bipolar disorder were re-evaluated to examine their profiles and differential diagnoses. Seventy-two percent satisfied DSM-III-R Bipolar Disorder criteria and most presented with manic or mixed mood symptoms. Half were psychotic. Non-affective psychosis, unipolar depression, organic syndromes and disruptive behavioral disorders complicated the differential diagnoses, particularly among younger boys. The well-documented bipolars were characterized by affective symptoms prior to the first admission and shorter hospitalizations than the remaining subjects. A recent trend towards overdiagnosis of bipolar disorder is suggested in some patients.