Recently, provisional research criteria for “schizo-affective” and related psychoses were published by the St. Louis Group. These rigorous criteria were modified and expanded for purposes of the present study in order to analyze the case records of 83 first admissions of Schneider-positive schizophrenics, that is, those with first rank symptoms, hospitalized in a strongly Schneider-oriented German University Clinic during the period 1962–1971. Research diagnosable “schizo-affective” disorder was thus found in 27.7 % (23 cases) of these patients; 12 of the 23 satisfied “full” affective research criteria for depression or mania, whereas 11 fulfilled “adjusted” affective criteria geared to cover more “labile” mixed mood states. Moreover, 48.2 % (40 cases) and 25.3 % (21 cases) of the sample were research-positive for “schizophreniform” illness and “atypical schizophrenia” respectively. Findings such as these suggest that “first rank” schizophrenia, as routinely diagnosed in Germany, may not be all that homogeneous a clinical entity.