It has been demonstrated that total parenteral nutrition (TPN) modulates the function of the hepatic reticuloendothelial system (RES). The objective of this study was to evaluate the impact of two different TPN lipid emulsions on the recovery of allograft RES function after orthotopic liver transplantation (OLTx). In a prospective, double-blind study, OLTx patients were randomly assigned to two treatment groups. Group I (n = 13) received a TPN regimen that included longchain triglycerides (LCT). Group II (n = 9) received a TPN regimen that included a fat emulsion consisting of both medium-chain triglycerides (MCT) and LCT. At baseline, i.e., on days 2 or 3 after OLTx (t1), before lipids for TPN were started, hepatic RES function was determined using the human serum albumin millimicrosphere technique (K-value, 1/min). A second measurement (t2) was obtained after 7 days of TPN, including one of the study's two fat emulsions. The mean (± SD) K-value (1/min) was 0.48 ± 0.16 in the LCT group and 0.55 ± 0.28 in the MCT/LCT group at t1, and it improved to 0.62 ± 0.21 in the LCT group and to 0.86 ± 0.32 in the MCT/ LCT group at t2. RES function recovery was significantly better in the MCT/LCT group (P ≤ 0.05). MCT/LCT emulsion appears to be the TPN fat emulsion of choice after OLTx as it seems to have less impact on hepatic RES recovery.