Because of the increased interest in the diets of children and adolescents and the possible relation between those diets and adulthood diseases, we reviewed nutritional assessment methods used specifically in young people. The assessment of diets of individual children and adolescents has evolved from Hasse's study of Swiss and Russian girls in 1882 to Burke's development of the dietary history to the Ten State Nutrition Survey. Currently, various government-sponsored surveys and several other assessment programs are studying the nutritional status of children and adolescents. We discuss the methods used in these investigations, compare the available dietary assessment tools (the dietary record, 24-h dietary recall, and food-frequency questionnaire), describe the development of a new food-frequency questionnaire (the Youth-Adolescent Questionnaire), and review new approaches. The data emerging from reproducibility studies suggest that food-frequency questionnaires provide enough accuracy in studies of adolescents to permit individual diets to be related to subsequent health outcomes.