Milk is promoted as a healthy beverage for children, but some investigators believe that estrone and whey protein in dairy products may promote weight gain. In this study of more than 12 000 offspring of people enrolled in the Nurses’ Health Study, children who drank more than 3 servings of milk per day increased their body mass index more than those who drank less milk. Drinking 1% or skim milk was also associated with increases in body mass index. The added calories from the larger amount of milk consumed appeared to be responsible for the increase in body mass index in these children. Drinking high amounts of milk, as with other beverages, may provide excess calories to some children, contributing to the increase in obesity in the United States.