The nutritional approach to the treatment of atherosclerosis was tested in 100 patients with proved coronary atherosclerosis. Fifty patients were treated with a low-fat, low-cholesterol diet. The other 50 patients were not given any specific treatment and acted as controls. By the end of 12 years, 19 of the 50 patients treated with the diet survived. Of the 50 control patients, all had died by the 12th year of observation. The total daily fat intake in this diet was 25 Gm. Animal fats were eaten in minimum quantities. Large-scale trial under controlled statistical conditions encountered in clinical practice is suggested for further evaluation of the role of fat in coronary atherosclerosis.