Lipids have been investigated in three groups of patients with chronic renal insufficiency. 19 patients were on conservative treatment (no dialysis), 52 patients were on regular hemodialysis, and 27 patients had been transplanted. The results were compared with those obtained from control subjects of the same age and sex. Hyperlipoproteinemia was found in 25% of the uremic patients, 55% of hemodialysis patients, and 85% of transplant recipients. The predominant lipid abnormalities were hyperlipoproteinemia of Type IV in both uremic (5 out of 19) and hemodialysis patients (17 ou of 52). Hyperlipoproteinemia of Type II was mainly observed after transplantation (IIb: 13, IIa: 5 out of 27).