Abstract: The effect of consumption of palm oil diets on plasma activities of some enzymes used as markers of organ function was investigated in rats. Four-week old male albino rats of the Wistar strain (n = 8 per group) were maintained for 28 days on standard dry rat food (4.7% fat by weight) supplemented (10% and 20% by weight) with red palm oil (RPO), refined palm olein (REFPO) and corn oil (CO). In the study, the effects of the various dietary supplements on plasma activities of lipase (EC 3.1.1.3), alkaline phosphatase (EC. 3.1.3.1), aspartate transaminase (EC 2.6.1.1) and alanine transaminase (EC 2.6.1.2) were compared with those of a control group receiving normal rat mash. The enzyme activities in the plasma of rats fed 10% oil-supplemented diets were comparable to those of the control (p>0.05). Plasma enzyme activities indicated dose-effect relationships between the amount of oil in the diet and activities of lipase, alkaline phosphatase (ALP) and alanine transaminase (ALT). The 10% oil-supplemented groups had significantly higher (P< 0.05) lipase activities (201.60 - 233.80 U/L) than the 20% oil-supplemented dietary groups (147.80 - 165.20 U/L). Alkaline phosphatase levels in test groups (65.70 - 94.46 U/L) were higher than those of the control (63.76 U/L). Increasing the fat contents of the diets induced significant increases (p< 0.05) in ALP activities. The aspartate transaminase (AST) levels of the control and 10% dietary groups (53.75-68.25 U/L) were higher than those of the 20% oil dietary groups (32.80 - 33.60 U/L). The activities of ALT in the experimental animals decreased with the levels of oil in the diet in a dose - dependent manner. Generally the activities of the transaminases assayed in the 20% oil-fed rats were significantly lower (p< 0.05) than those of the control. A determination of ALT/AST ratios indicated values lower than unity in all experimental animals, though the values for 20% oil groups were higher than those of the control and 10% groups. The effects of palm oil containing diets on enzyme profile were comparable to those of corn oil containing diets, as were the effects of RPO when compared with those of REFPO. The results indicated that consumption of palm oil (red or refined) in moderate amounts supports normal enzyme activities.