Total cholesterol levels, obesity index and blood pressure were measured in 6,278 school-age children living in Ibaraki Prefecture in 1991, and children with high risk for atherosclerosis were identified. The frequencies of the school-age children with hypercholesterolemia (total cholesterol > or = 200 mg/dl), obesity (obesity index > or = 40%) or hypertension were 7%, 5%, 1%, respectively. In half of the area where the children lived, lipid measurements were also obtained in the parents of hypercholesterolemic children. Twenty-nine out of ninety fathers (32%) and 22 out of 140 mothers (16%) were hypercholesterolemia (total cholesterol > or = 240 mg/dl). Among them five families of familial hypercholesterolemia were diagnosed. Seventy children with hypercholesterolemia and 81 obese children, who were screened and received health counseling, were re-examined after one year. The levels of LDL-cholesterol, triglyceride and atherogenic index were significantly decreased and HDL cholesterol level was significantly increased in the children with hypercholesterolemia. Obesity index, triglyceride level and atherogenic index were significantly decreased and HDL cholesterol level was significantly increased in the children with obesity. In addition, the frequencies of the children with dyslipidemia or liver dysfunction were significantly decreased in the obese children after one year. These data suggested that the screening system and the plans after the examinations described here were effective in reducing risk factors for atherosclerosis in children.