The investigation has been carried out on cultures grown in the presence of 5×10^(-1)-5×10^(-5) M acrylonitrile with or without a rat liver metabolizing system (S-9 mix). The results obtained showed that acrylonitrile was toxic starting from the 5×10^(-3) M concentration, caused a significant increase in the sister chromatid exchange (SCE) frequency in comparison with the controls (p≤0.00l) when the concentration was 5×10^(-4) M, and elicited reparative deoxyribonucleic acid (DNA) synthesis, determined by tritiated thymidine uptake, particularly when the concentration was 5×10^(-1) M. These effects were observed in lymphocytes of different donors and after drug activation by the S-9 mix metabolizing system.