Hemodialysis patients display increased oxidative damage to red blood cell (RBC) membranes, characterized by elevated levels of malonyldialdehyde (MDA), a short chain aldehyde produced by the oxidation of the polyunsaturated fatty acids (PUFA) in the RBC membranes. This is the result of a metabolic blockage of the pentose-phosphate shunt in uremic patients, which causes reduced detoxification of highly oxidative free radicals. The oxidative damage induces increased RBC rigidity and decreased RBC deformability, therefore favoring hemolysis. The aim of this work was to determine if a functioning renal graft would restore normal erythrocyte metabolism, reducing the oxidative damage. To this end, we have determined RBC MDA concentrations in 20 hemodialysis (HD) patients (RBC MDA 18.22 +/- 4.36 micrograms/ml packed RBC), 20 renal transplant (T) patients with well functioning grafts (serum creatinine less than 2 mg%) (RBC MDA 1.2 +/- 0.4 micrograms/ml packed RBC) (T vs. HD P less than 0.005) and 20 healthy controls (HC) (RBC MDA 1.44 +/- 0.6 micrograms/ml packed RBC) (HC vs. HD P less than 0.005; HC vs. T NS). Our findings show that a well-functioning renal graft restores normal RBC metabolism and eliminates the oxidative damage induced by uremia.