The possible effect of diet on plasma lipids was investigated in a group of vegetarians. Seventy-three men and 43 women who had adhered to a vegetarian diet for an average of three years were studied in the fasting state and compared with a randomly selected group of controls matched for age and sex. Mean cholesterol levels in milligrams per deciliter for vegetarians and controls, respectively, were 126 and 184; low-density lipoprotein, 73 and 118; very-low-density lipoprotein, 11.8 and 17.2; high-density lipoproteins, 42 and 49; and mean triglyceride levels 59 and 86. Mean weight and subscapular skinfold thicknesses were 58 kg and 6 mm for vegetarians and 73 kg and 17 mm for controls. Similar differences in lipid levels were found between subgroups of 42 vegetarians and controls with identical mean weights. Multiple regression analyses showed that consumption of dairy foods and eggs, but not body weight, was associated with the lipoprotein and cholesterol findings.