In adult populations, elevated blood pressure is related to the development of stroke, renal disease, and occlusive atherosclerosis. The significance of blood pressure levels in childhood, unless extremely elevated, has not been related to disease outcomes. In a study carried out in Muscatine, Iowa, the risk of high blood pressure in young adult life was evaluated based on the observations of blood pressure and other factors made during the school-aged years. Subjects, 2445 in number, were first observed at ages 7 through 18 years and again between 20 and 30 years. During childhood, measurements of blood pressure, height, and weight were made on alternate years. At adult ages, the same measurements were again made and a health questionnaire was administered. Adult blood pressure was correlated with childhood blood pressure, body size, and change in ponderosity from childhood to adult life. Adult ponderosity was related to childhood ponderosity, and those who were most obese as adults showed the greatest increase in weight from their childhood years. These observations suggest that strategies to prevent the acquisition of excess ponderosity during childhood may be useful in preventing adult hypertension.