This investigation provides updated information on the onset of stuttering, explores variations in the onset, and studies possible relationship of stuttering onset to the factors of age, gender, familial history, severity, and stress. Data were obtained for 87 preschool children through parent interviews, using a standardized questionnaire. Interviews were conducted within 12 months after the disorder was first diagnosed. Results for selected items indicated that onset tended to occur at an earlier age than was previously thought and was sudden and/or severe in a substantial number of cases. Physical or emotional stress and familial histories of stuttering were reported for many of the participating children. A significant gender factor was found. About twice as many boys as girls stuttered and girls began stuttering at a significantly earlier age. There was a positive relationship between severe stuttering and sudden onset. Several other tendencies for relationship between factors were either weak or not significant for the present sample size. The findings are discussed with special reference to the possible relationship between stuttering onset and maturational processes and the possible contribution of data on onset to the differentiation of stutterers.