The initial survey in 1973-1974 was restricted to children ages 2 1/2 to 14. A physical examination was conducted and information was collected on anthropometric data, hemoglobin, blood pressure, serum lipids, and health history. Over 3,500 children participated. The second cross-sectional survey of 1976-1977 and subsequent surveys expanded the eligible population to include all children ages 5-17 years. The second survey of over 4,000 children also included information on salt intake, smoking, health beliefs, and attitudes, and for girls ages 8-17, menstrual history and oral contraceptive use. The third survey of over 3,500 participants in 1978-1979 also collected anthropometric measurements on skinfold thickness and two measurements of heart rate. The fourth survey of over 3,300 participants in 1981-1982 added data on alcohol use, Type A behavior, peer networks and dieting habits.