Objective To investigate the effects of lipnsomal prostnglandin E1 (Lipo-PGE1) on the renal function in patients undergoing cardiopulmonary bypass (CPB) .Methods Twenty ASA Ⅱ or Ⅲ patients of both sexes aged 34-56 yr weighing 48-81 kg scheduled for elective cardiac valve replacement with CPB were randomly divided into 2 groups (n = 10 each): normal saline group (group NS) and Lipo-PGE1 group. In group Lipo-PGE1, Lipo-PGE1 was infused at 3 ng·kg-1·min-1 from the initiation of CPB to the end of CPB, and then added into the priming solution of the extracorporeal circulation machine with its concentration set at 5 ng/ml. In group NS, the equal volume of normal saline was administered instead of Lipo-PGE1 . The concentrations of thromboxane B2 ( TXB2 ), 6-keto-prostnglandin F1α ( 6-Keto-PGF1α ), and free hemoglobin ( F-Hb ) in plasma, and α1-microgipbulin (α1-MG), β2-micmglobulin (β2-MG) and Cystatin C (Cys C) in serum were measured after heparinization and before CPB (T1), at 30 min of CPB (T2) and at 0, 1 and 24 h after termination of CPB (T3-5). Results Compared to T1, the concentrations of TXB2, 6-Keto-PGF1α, α1-MG and β2-MG and TXB2/6-Keto-PGF1α ratio at T2-4, and the concentrations of F-Hb and Cystatin C at T2-5 were significantly increased in both groups ( P < 0.05). The concentration of 6-Keto-PGF1α at T2-4 was significantly higher, and concentrations of TXB2, α1-MG and β2-MG and TXB2/6-Keto-PGF1α ratio at T2-4 and concentrations of F-Hb and Cys C at T2-5 were significantly lower in group Lipo-PGE1 than in group NS ( P < 0.05). Conclusion Lipo-PGE1 can obviously improve the renal function in patients undergoing CPB.