Vascular disease is a major cause of morbidity and mortality in end stage renal failure patients and cannot be explained entirely by the prevalence of traditional risk factors for atherosclerosis. A high plasma homocysteine concentration, which is a risk factor for vascular disease is found in patients with end stage renal disease. The exact cause for the hyperhomocysteinaemia seen in these patients is unknown, but is probably related to altered renal metabolism of homocysteine. High homocysteine concentrations may also be attributable to a deficiency of folate, vitamin B6 or vitamin B12 although, because of supplementation, these vitamins may be present in high concentrations in renal patients. The occurrence of hyperhomocysteinaemia despite high plasma vitamin concentration could be due to altered metabolism or inhibition of intracellular vitamin activity. A number of studies have now established hyperhomocystinaemia to be an independent risk factor for atherosclerosis in patients with end-stage renal disease. Plasma homocysteine concentrations can be reduced by administration of folic acid either alone or combined with vitamin B12 or vitamin B6. The effects of such reduction on vascular risk in renal failure patients needs further study.