For 3 mo, 14 patients with severe coronary heart disease and serum cholesterol levels of 6-9.5 mmol/l were treated with a diet containing 10% of total energy from fat and less than 100 mg cholesterol per day. Serum cholesterol and serum low-density lipoprotein (LDL) cholesterol were reduced by 33% and 41%, respectively, while serum high-density lipoprotein (HDL) cholesterol and serum triglycerides did not change significantly. After 3 mo, patients were asked to maintain a diet as low in fat as possible for long-term treatment. After 12 mo, a 4-day diet recall showed a mean fat intake of 21.4% (range 7.3-37.8%). On average, serum cholesterol and serum-LDL cholesterol were reduced by 14% and 18%, respectively, from pretreatment values. Serum triglycerides decreased by 27% and serum-HDL cholesterol increased by 18%. At month 12 serum cholesterol and changes in serum cholesterol were correlated to the consumption of fat.