The study examines two levels of physical abuse of children as measured by the 'minor,' 'severe' and 'very severe' violence indices of the Conflict Tactics Scales. The subjects ranged in age from birth through 17 years. Findings indicate that 90 percent of the parents used physical punishment, which peaked at ages 3 to 4, then decreased steadily. More than half of all parents still used physical punishment at age 13. No age trend was found for very severe violence. Parents who used any level of violence tended to do so repeatedly. Boys were victims more than girls and more blue-collar parents than white-collar parents engaged in both minor and severe violence. These effects were stronger for severe violence. Mothers used minor violence more often than fathers. Only one significant interaction effect was found. Several explanations, particularly social norms, are used to interpret these findings. Tabular data, 10 footnotes, and 54 references. (Author abstract modified)