Disaturated (fully saturated) lecithins adsorb onto solid surfaces more readily than lecithins in which one or both fatty acids are unsaturated. If saturated lecithins adsorb to arterial walls as they do to glass and polystyrene surfaces, there may be increased probability of atherosclerosis when the disaturated lecithin content of plasma is elevated. Analyses of lecithins in plasma samples from patients with myocardial infarction, and from patients with premature atherosclerosis but with low concentrations of plasma cholesterol and triglycerides, are consistent with the hypothesis that a high concentration of disaturated lecithin in plasma may be a significant risk factor for atherosclerosis, independent of triglyceride and cholesterol concentrations.