Obese children may be at increased risk of becoming obese adults. To examine the relationship between obesity in childhood and obesity in adulthood, we reviewed the epidemiologic literature published between 1970 and July 1992. Comparison between studies was complicated by differences in study design, definitions of obesity, and analytic methods used. Although the correlations between anthropometric measures of obesity in childhood and those in adulthood varied considerably among studies, the associations were consistently positive. About a third (26 to 41%) of obese preschool children were obese as adults, and about half (42 to 63%) of obese school-age children were obese as adults. For all studies and across all ages, the risk of adult obesity was at least twice as high for obese children as for nonobese children. The risk of adult obesity was greater for children who were at higher levels of obesity and for children who were obese at older ages. The wide range of estimates in this literature are, in part, due to differences in study designs, definitions of obesity, ages at which participants were measured, intervals between measurements, and population and cultural differences.