Elevated plasma homocysteine levels are a risk factor for atherosclerotic disease. Elevated fasting plasma homocysteine concentrations can be reduced by vitamin supplementation with folic acid, vitamin B6 and vitamin B12, but the effect of nutritive amounts of single vitamins on homocysteine plasma levels within the normal range is not known. This study was performed to investigate the effect of folic acid supplementation (400 micrograms/d) on fasting plasma homocysteine levels in healthy young women, in comparison to vitamin B6 (2 mg/d) or a combination of both vitamins. Healthy young women with normal homocysteine levels were supplemented for four weeks either with folic acid, vitamin B6 or the combination. The combination of folic acid and vitamin B6 reduced plasma homocysteine by 17%. Supplementation with folic acid reduced plasma homocysteine levels by 11.5%. The effect of folic acid and vitamin B6 was not significantly different from the effect of folic acid alone. Vitamin B6 had no effect on plasma homocysteine concentrations. Results show that homocysteine levels within the normal range are lowered by low-dose vitamin supplementation including folic acid.