• Eighty-five cases of atypical schizophrenia were compared with 200 of schizophrenia, 100 of bipolar (mania), and 225 of unipolar (depression) affective disorder. Comparisons were made on the basis of sex, age at admission, precipitating factors, outcome, and a family history of schizophrenia or of affective disorder. The atypical schizophrenia differed remarkably from the schizophrenia and most closely resembled the bipolar affective disorder when allowance was made for a younger age at onset and a higher frequency of precipitants. An analysis of symptoms verified the predominance of schizophrenic features in the atypical schizophrenia, but also showed a high percentage (80%) of patients who had one or more manic symptoms at index admission. It is concluded that great care should be taken in diagnosing schizophrenia in a patient who also has manic symptoms.