A mixture of dietary saturated fatty acids raises the serum total cholesterol concentrations compared with a diet of isoenergetic amounts of carbohydrates. Saturated fatty acids are not all equally hypercholesterolemic: stearic acid (18:0) and saturated fatty acids with < 12 carbon atoms are thought not to raise serum cholesterol concentrations. This suggest that the cholesterol-raising properties of saturated fatty acids should be attributed solely to lauric acid (12:0), myristic acid (14:0), and palmitic acid (16:0). These three saturated fatty acids, however, may have different effects on serum total-cholesterol concentrations as well. Results from controlled dietary experiments suggest that lauric acid (12:0) is less, and myristic acid (14:0) probably more, hypercholesterolemic than palmitic acid (16:0). Effects of the different saturated fatty acids on the distribution of cholesterol over the various lipoproteins are largely unknown, but it is suggested that stearic acid lowers HDL cholesterol concentrations relative to other saturated fatty acids. At present, however, too many questions are unanswered to quantitate these differences.