One hundred young male outpatients with coronary disease who were under dietary management with a 28% fat diet were group-matched to a non-dietary-managed group in regard to age, age at infarction, number of infarctions, prevalence of hypertension, degree of angina, and value of serum cholesterol, among other factors. The diet-managed group experienced a significant reduction in serum cholesterol value, while the non-dietary-managed group did not. No significant differences were noted between the two groups in levels for serum total lipids, phospholipids, and triglycerides. Under the experimental conditions employed, the degree of unsaturation of the diet did not appear to influence serum cholesterol value or mortality. The non-dietary-managed group had a 160% higher recurrent infarction rate and a 233% higher mortality rate than did the dietary-managed group during the first five years of observation.