This study is concerned with coronary risk factors in school age children in Muscatine, Iowa. Measurements of heights, weights, triceps skin fold thickness, cholesterol and triglyceride levels, and blood pressure have been made on alternate years in an entire school district on alternate years since 1970. From these measurements studies of tracking (peer rank order consistency) of anthropometric measures, lipids and blood pressure have been described. Children whose blood pressure remain persistently in the upper quintile, mid quintile and lowest quintile of the distribution have been studied. These have been studied by echocardiography, and venous occlusive plethysmography. Children in the upper part of the distribution of blood pressure have higher cardiac outputs, and equal vascular resistance to those in the lower part of the distribution of blood pressure. Those in the upper part of the distribution have significantly thicker interventricular septa and left ventricular posterior walls than those with lower pressures. Those with higher pressures also show an inability to maximally vasodilate their forearm vascular beds to the same degree as those with lower pressures. These observations indicated that children with higher blood pressures have thicker hearts and structurally different systemic vascular resistence beds.