Hyperhomocyst(e)inemia is a probable contributor to the excess atherosclerosis of patients with chronic renal failure on dialysis. Although treatment with folate 2 mg daily is usually effective in normalizing plasma homocyst(e)ine (H(e)) in patients with normal renal function, higher doses of folate or other approaches to treatment may be necessary in renal failure. There is no agreement among dialysis units regarding the ‘correct’ dose of folate supplementation; routine doses range from 1 to 5 mg daily. To determine whether one of these doses is more effective, we compared H(e) in 55 hemodialysis taking 1 mg folate versus 73 patients taking 5 mg folate daily at two dialysis units. In the group as a whole, mean H(e) was 28.23 ± 17.49, significantly higher than in a group of 290 volunteers with normal renal function 12.31 ± 6.17 (p = 0.0001). H(e) levels were 28.93 ± 16.79 μmol/l on 5 mg folate and 27.31 ± 18.49 on 1 mg; p = 0.61. There was no significant relationship between adequacy of dialysis (K<sub>t</sub>/V) and H(e). In a small group of peritoneal dialysis patients, H(e) was significantly lower at 18.8 ± 7.89 (p = 0.026), but further study is required in a larger sample to confirm that observation. It appears that routine doses of folate in use in dialysis units are not sufficient to reduce H(e) to levels associated with average cardiovascular risk; new approaches to treatment of hyperhomocyst(e)inemia in dialysis patients are required.