Serum lipids, apoprotein and lecithin-cholesterol acyltransferase activities were studied in 27 renal transplant recipients with stable and normal renal function (serum creatinine 0.16 mM/1 or less) sustained for more than 1 year following grafting. Hypertriglyceridemia, which was characteristic of hyperlipidemia in 18 hemodialyzed patients with chronic renal failure, was no longer manifest in transplant recipients. On the other hand, de novo hypercholesterolemia was observed posttransplant with mean serum levels of 5.82 ± 1.34 versus 5.01 ± 0.88 mM/1 in 575 normal controls. As to the high-density lipoprotein metabolism, the cholesterol content (1.72 ± 0.56 mM/1) was significantly higher in transplant patients than in hemodialyzed patients (0.82 ± 0.31 mM/1). In contrast, no variation in apoprotein A-I levels was found between both groups of patients, which produced an elevated high-density lipoprotein cholesterol: apoprotein A-I ratio. Thus, derangement in the serum lipid profile, although qualitatively different, continued to be present following transplantation, and its relevance to the cardiovascular morbidity in these patients remains to be evalua