1. The recovery of lipid metabolism was investigated in paediatric patients treated for terminal liver disease by liver transplantation from living related donors. 2. The cholesterol ester ratio (esterified cholesterol/total cholesterol) and the total cholesterol/phospholipid ratio increased from preoperative values of 0.35 +/- 0.04 and 0.59 +/- 0.03 to 0.65 +/- 0.01 and 0.68 +/- 0.01 at 3 weeks after liver transplantation in successful cases (means +/- SEM, n = 26), respectively, whereas these two parameters decreased in failed cases (n = 4). 3. Biochemical analysis indicated that weekly recoveries in the cholesterol ester ratio and the total cholesterol/phospholipid ratio are characteristic of successful liver transplantation with a graft from a living related donor.