The parents of one hundred thirty-four children under five were studied in detail over a two-year period and compared with a control group, in order to assess the importance of various social stresses and to separate factors typical of low social class from those specific to baby batterers. Lack of family cohesiveness as an important factor was suggested by the findings. Absence of the father from the home was common to one third of the cases. Factors associated with marital breakdown—such as marriage of the mother before age twenty, premarital conception, disagreement or disharmony in child rearing practices—were all common to index cases, as were neuroses among the mothers and personality disorders