 In this application, we propose to conduct a pilot, randomized, double-blinded, placebo-controlled trial to explore the use of prophylactic L-arginine supplement in preserving renal function in LTx recipients. Twenty-four 24 LTx recipients recovering uneventfully from the procedure will be recruited for the study. Subjects will be randomized 1:1 to receive 9g per day of L-arginine or placebo given orally for 7 days between 14 and 21 days after LTx, followed by open-label maintenance with L-arginine. The aims of the study are as follows: 