Recent studies have shown a consistent association between relatively low plasma concentrations of high-density lipoprotein (HDL) cholesterol and increased risk of coronary heart disease. A cross-sectional comparison was made of the distribution of plasma lipids and lipoproteins in groups of 41 male and 43 female long distance runners versus larger control groups matched for age and sex, randomly selected from northern California towns. The runners showed modestly lower total cholesterol concentrations, while their triglyceride levels were only 50% of control. HDL-cholesterol was higher in runners than controls (75 +/- 14 vs 56 +/- 14 mg/100 ml for women; 64 +/- 13 vs 43 +/- 10 for men), while low-density lipoprotein cholesterol was lower (113 +/- 33 vs 124 +/- 34 for women; 125 +/- 21 vs 139 +/- 32 for men). All differences were statistically significant (p less than 0.05), and only partially attributable to known factors other than high physical activity level. Since the runners were predominantly normotensive, relatively lean, and exclusively nonsmokers, they appear to constitute a remarkably favored group with respect to risk of cardiovascular disease.