The authors examined the records of 9 manic patients under age 21 and 12 over age 30 for the incidence of "schizophrenic" and manic symptoms. The adolescent patients had a higher incidence of each of the 10 schizophreniform symptoms rated and significantly more delusions and ideas of reference. Significantly more adolescent patients had 3 or more schizophreniform symptoms; they also had symptoms typical of mania. These findings highlight the diagnostic importance of affective symptoms in psychotic adolescents with mixed symptoms and raise important clinical and theoretical questions about the atypical clinical picture of manic-depressive illness in young patients.