Study was performed by counting cells with chromosomal aberrations in C57Bl/6 mice. Bark dry extract was given perorally in doses of 50, 150, 450, and 1500 mg/kg. Mutagens dioxidine and cyclophosphamide were injected intraperitoneally in doses of 200 and 20 mg/kg, respectively. Bark dry extract in doses of 150 and 1500 mg/kg did not possess cytogenetic activity. Bark dry extract in doses of 50, 150, and 450 mg/kg significantly decreased the cytogenetic effect of mutagens under various regimens of treatment with the preparation (single combined administration, 5-day pretreatment, and 5-day combined administration). Our results indicate that bark dry extract possesses antimutagenic properties.