Prior to the introduction of lithium, mania was underdiagnosed in the U.S.A. Almost 50% of adults who met DSM-III criteria for mania had previously been diagnosed to have schizophrenia. To determine if mania had similarly been underdiagnosed in prepubertal children, 157 cases of 'severely disturbed' children described in the literature were reviewed. Approximately one-half (16/33) of the children diagnosed in this study as manic according to DSM-III had originally received another diagnosis. These results indicate that mania should be considered in the differential diagnosis of psychotic children, particularly those with affective symptoms.