We examined the effect of the positional distribution of fatty acids within dietary triglycerides on serum lipoproteins. Sixty subjects consumed two diets of equal fatty acid composition for 3 wk each. In the palm oil diet 82% of palmitic acid was attached to the outer two carbon atoms of glycerol, and 18% to the middle carbon. In the diet rich in enzymatically modified palm oil these figures were 35% and 65%, respectively. On the modified-fat diet, average lipoprotein concentrations showed nonsignificant (P > 0.13) increases of 0.06 mmol/L for total, 0.03 mmol/L for HDL, and 0.04 mmol/L for LDL cholesterol compared with palm oil. The small increases in total and LDL cholesterol were statistically significant in the men (n = 23) but not in the women (n = 37). The ratio of HDL to LDL cholesterol and serum triglyceride concentrations were unchanged. Thus, a large difference in dietary fatty acid configuration had little effect on lipoprotein concentrations in humans.