Approximately 4,000 preschool black children from low-income families in South Memphis participated for three years in a supplementary food program sponsored by the US Department of Agriculture. Part of this group received additional benefit from food stamps, day-care centers, and an infant-feeding program. We evaluated the effects of this participation in 250 children selected randomly from the enrollment list of the supplemetary program. Each child was examined for height, weight, head circumference, and levels of hemoglobin, serum iron, and vitamins A and C. The data were then compared with those from a similar survey in the same area conducted three years before. The results of this comparison indicate considerable improvements in height and weight and a reduction in the incidence of anemia and in the numbers of children with low plasma vitamin A levels. In the absence of other recognizable intervening factors, we conclude that federal food assistance programs were primarily responsible for the observed nutritional improvements.