Both studies used nationally representative samples (2,143 familes in 1975 and 3,520 in 1985), and both found an extremely high incidence of severe physical violence against children ('child abuse') and a high incidence of violence against spouses. The 1985 rates were 47 percent lower for the child abuse rate and 27 percent lower for the wife abuse rate. Possible reasons for the lower rates are examined and evaluated, including: (1) differences in study methods; (2) increased reluctance to report; (3) reductions in intrafamily violence due to 10 years of prevention and treatment effort; and (4) reductions due to changes in American society and family patterns that would have produced lower rates of intrafamily violence even without ameliorative programs. The policy implications of the decreases and of the continued high rate of child abuse and spouse abuse are discussed. 71 references.