We studied the effect of dioxidine on genome-wide methylation in short-term cultures of peripheral blood lymphocytes derived from healthy donors. Methylation was evaluated in lymphocytes before culturing, after 25 h in culture, and 1 h after addition of dioxidine in two concentrations (0.1 and 0.01 mg/ml). The total time in culture was 25 h. The level of methylation was assessed using methyl-sensitive single-cell gel electrophoresis ("comet assay") with additional restriction with HpaII amd MspI. Significant individual differences were found in the levels of methylation in both native cells and in cells treated with dioxidine in both concentrations. Mean group indicators of methylation did not differ before culturing and after 25 h in culture (45.28 and 44.80%, respectively). The mean group rate of methylation increased to 46.14% (p<0.001) after dioxidine treatment in a concentration of 0.01 mg/ml. Dioxidine in 0.1 mg/ml reduced the level of methylation (mean group rate 42.31%; p<0.001).