To compare the relative impact of dietary lauric acid (12:0) and palmitic acid (16:0) on plasma lipids, two fat-sensitive species, Mongolian gerbils and cebus monkeys, were fed cholesterol-free, purified diets enriched with either 12:0-rich or 16:0-rich fats, while all other fatty acids were held constant by selective blending of up to five natural fats or oils. The two gerbil diets (40 en% from fat) allowed for an 8 en% exchange between 12:0 and 16:0, and the monkey diets (31 en% from fat) allowed for 6 en% exchange between these two fatty acids. Eight gerbils received the diets for eight weeks, and 12 cebus monkeys were fed each diet in a cross-over design for up to 22 wk. Both diets resulted in similar plasma cholesterol, triglyceride, and high density lipoprotein cholesterol concentrations within each species. Additionally, separation of cebus lipoproteins by discontinuous density-gradient ultracentrifugation failed to show any dietary differences in concentration or composition of the three major lipoprotein classes (d < 1.019, 1.019-1.055, and 1.055-1.168 g/mL). Thus, in two species sensitive to manipulations in dietary fat while consuming cholesterol-free diets, 16:0 was not hypercholesterolemic relative to 12:0.