Higher plasma homocysteine concentrations can influence genomic DNA methylation in peripheral blood cells. In the present controlled study we observed a significant increase (10%) of genomic DNA methylation in patients with alcoholism (t = -3.16, df = 158, p = 0.002) which was significantly associated with their elevated homocysteine levels (multiple linear regression, p < 0.001). Since methylation of DNA is an important epigenetic factor in regulation of gene expression these findings may have important implications for a possible subsequent derangement of epigenetic control these patients.