In the light of recent breakthrough in the study of schizophrenia indicating a far stronger genetic factor than has been previously suspected, the role of heredity in stuttering is critically reexamined. Present knowledge of the role of heredity in stuttering springs from four principal data sources: (1) studies of familial incidence; (2) spontaneous recovery studies; (3) twin studies; and (4) studies of parental disfluency. It is hypothesized that the 4:1 sex ratio in stuttering may be the product of selective genetic factors. Critical examination of earlier and more recent studies leads to substantial evidence that a familial predisopsing factor exists in about 25% cases of stuttering.