In the latest years it became clear that beside traditional cardiovascular risk factors the high plasma homocysteine level increases the risk of atherosclerotic diseases too. Metaanalysis of 27 papers found that 10% of population's coronary risk is attributable to homocysteine and a 5 mumol/l increase in its plasma level elevates the coronary risk by as much as 0.5 mumol/l cholesterol increase. Recent studies have shown an inverse relation between the levels of plasma homocysteine and that of folic acid, vitamin B6, vitamin B12. The latters are cofactors and substrates of the homocysteine and methionin metabolism. The plasma total cholesterol, HDL-cholesterol, triglyceride, lipoprotein(a), Apo A1, Apo B and homocysteine concentrations were examined in 39 patients suffering from coronary artery disease treated in the Cardiac Rehabilitation Department of our hospital. Twenty of them were treated by folic acid and vitamin B6 for a three week period. The mean (+/- SD) plasma homocysteine concentration was 15.60 +/- 6.14 mumol/l. In the treated subgroup the mean (+/- SD) plasma homocysteine concentration was 17.3 +/- 7.00 mumol/l, the mean (+/- SD) plasma folic acid level was 8.58 +/- 4.6 mumol/l. After the three week treatment period (folic acid and vitamin B6) the plasma homocysteine level decreased by 26.5% (p = 0.012), that of folic acid increased by 68.7% (p = 0.002). From the plasma lipids the level of total- and LDL-cholesterol decreased significantly (6.7% and 10.4%, P < 0.05), caused by the strict diet during hospital treatment. As for the genetic polymorphism of the V677 gen of the metylenetetrahydrofolate-reductase (MTHFR) enzyme there was a significant correlation with homocysteine level (r = 0.436, p = 0.010), and a negative, but not significant correlation with the folic acid level (r = -0.354).