Serum lipoprotein(a) (Lp(a)) was measured in 101 men with end-stage chronic renal failure (CRF) receiving haemodialysis and in 101 age-matched male controls. Apolipoprotein(a) genetic polymorphism was determined by immunoblotting in 100 patients and in 92 controls. Patients with CRF on haemodialysis had significantly greater serum Lp(a) than controls. Apolipoprotein(a) phenotype frequencies in patients with CRF did not differ from those of the control group. Both patients and controls with phenotype S2 had greater serum Lp(a) than those with phenotype S4. It should be emphasized that serum Lp(a) was significantly greater in patients on haemodialysis than controls, both for those with phenotype S2 and those with S4. Increased serum Lp(a) together with other lipoprotein abnormalities in patients with CRF on haemodialysis imply an increased cardiovascular risk. Genetic polymorphism clearly influences serum Lp(a) both in controls and patients. In the latter group CRF itself, dialysis, or both, also play a role in increasing Lp(a).