The influence of dairy foods in the diet on plasma levels of total, low-density lipoprotein, and high-density lipoprotein cholesterol (TC, LDL-C, and HDL-C, respectively) was studied in 75 adult lactovegetarians living in the northeastern United States. Dairy products were the major sources of dietary saturated fat and cholesterol. The plasma TC level was positively correlated with dietary saturated fat and dietary cholesterol, and inversely correlated with the ratio of polyunsaturated to saturated fats in the diet. Correlations between the LDL-C level and the nutrients were similar to those of the TC level. The HDL-C level was not significantly related to any nutrients in the diet. The cholesterol levels of the lactovegetarians were compared with those of strict vegetarians. Lactovegetarians had 24% higher LDL-C levels and 7% higher HDL-C levels than strict vegetarians. Analysis within and among vegetarian populations suggests that ingestion of fatty dairy products raises the LDL-C level on a percentage basis about three times more than it raises the HDL-C level.