This study compared the rate of physical abuse of children from a 1975 study with the rates from a 1985 replication study. Both studies used nationally representative samples (2,143 families in 1975 and 3,520 families in 1985), and both found an extremely high incidence of physical assaults against children which were severe enough to constitute child abuse. Although the 1985 rates were high, they were substantially lower than the 1975 rates. There was a 47% decrease in physical child abuse reported from 1975 to 1985. Possible reasons for the decrease include: (1) differences in the methods of the studies; (2) increased reluctance to report incidents of child abuse; (3) reductions in intra-family violence due to 10 years of intensive prevention and treatment efforts; and (4) reductions due to changes in American society and family patterns which would have produced lower rates of intra-family violence even without ameliorative programs. Most likely the findings represent a combination of changed attitudes and norms, and changes in overt behavior. This interpretation is based on changes in American society in the areas of the family, the economy, the social acceptability of family violence, alternatives available to women, social control processes, and the availability of treatment and prevention services. (Policy implications of the decreases and of the continued high rate of child abuse, are discussed.) (Author/NB)