Folic acid (FA) supplementation reduces the elevated serum homocysteine (Hcy) concentrations. 6 S-5-methyltetrahydrofolate (6 S-5-MTHF) is an alternative to FA due to possible advantages, that is, no masking cobalamin deficiency. The study aim was to evaluate the effectiveness of 6 S-5-MTHF in relations to FA supplementation in reducing the serum Hcy. Healthy volunteers, aged 50-65, had normal serum folate and did not use supplements with B-vitamins for 6 months. Forty subjects were divided into two groups: receiving 400 μg/d FA or the equimolar amount of 6 S-5-MTHF. Blood was collected at baseline and after 4 weeks. In both groups, a significant decrease in the mean Hcy level after intervention period was observed. Supplementation with 6 S-5-MTHF was slightly less effective, but not significantly, in Hcy lowering than FA (p = .243 between the groups), that is, by 7.8% and 13.4%, respectively. The 6 S-5-MTHF was shown to be an adequate alternative to FA in reducing Hcy concentrations.