Age at onset and sex differences in the age at onset were investigated in the schizophrenic subtypes of 200 patients. Significant differences in the age at onset were observed among these subtypes; the disorganized subtype demonstrated the earliest and the paranoid the latest onset. The mean age at onset of all female patients was significantly greater than that of the male. Specifically, in the paranoid subtype the onset for men occurred earlier than for women. Conversely, in the disorganized subtype the disorder appeared earlier in women. There was no significant sex difference in the age at onset in the undifferentiated and the residual subtypes. In the paranoid subtype most men developed the disease before age 30 (72%), whereas women had an even distribution of the onset before and after 30. Ninety-six patients admitted for the first time demonstrated findings similar to those of the total sample. The data provide additional information on the phenotypic expression of the subtypes of schizophrenic disorders and indicate the necessity for further demographic and genetic studies to delineate the underlying defect.