Following liver transplantation, the effect of post-operative parenteral nutrition with MCT LCT (Medium Chain Triglycerides/Long Chain Triglycerides) fat emulsions on the recovery of allografts RES function was investigated in a randomised prospective study of three groups of patients (group I, n = 14: 50g MCT LCT fats twice weekly, group II, n = 15: 0.7 g/kg body weight per day MCT LCT fats, group III, n = 17: 1.5 g/kg body weight per day MCT LCT fats). RES function was assessed using the ^99mTc-HSA-MM-Clearance (^99mTechnitium-Human serum albumen-Millimicrosphere-Clearance). There were no statistically significant differences in the recovery of RES function between the groups. A negative effect on RES function as a result of the administration of MCT LCT fat emulsions up to 1.5 g/kg b.w. per day can therefore be excluded. The evaluation of liver biopsies before the administration of fats and at the end of TPN (Total Parenteral Nutrition) showed no evidence, in the 20 patients investigated, of any fatty changes in the liver caused by the infusion of fat.