Eighty-five cases of atypical schizophrenia were compared with two hundred of schizophrenia, one hundred of bipolar (mania), and two hundred twenty-five 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.