CATCH consisted of a three-and-a-half year feasibility study conducted from September 1987 through March 1991, the main trial beginning in April 1991, and the Tracking Study, in 1996 a follow-up study to allow measurements on the cohort through ages 13 to 14 years. The purpose of the feasibility study was to test the acceptability of the interventions and measurements in 1,471 third, fourth, and fifth grade boys and girls, ages 7 to 11. The main components of the Phase I intervention programs at the eight schools included classroom curricula for the third, fourth, and fifth grades; home curricula designed to involve parents and children in CATCH activities at home and family fun nights to enhance family involvement; a physical activity program centered around a new physical activity curriculum; and a school nutrition program for school food service directors and staff. Blood samples were obtained from 1,045 children during risk factor screening. Other measurements included blood pressure, height, weight, triceps, and subscapular skinfolds. Nutrient intake was pilot-tested with an interactive 24-hour recall approach, supplemented by food records, a home food inventory, and follow-up calls to parents. Physical activity was measured with a physical activity interview and the Caltrac motion sensor.