Аннотация:The influence of antitumor drug ftorafur (Ft) on the frequency of gene mutations to 8-azaguanine resistance was investigated. Asynchronous and synchronized cultures of SV40 transformed Djungarian hamster cells were used. The 2 to 3,5 fold increase in the frequency of gene mutations over the control level was observed after the Ft treatment. The most pronounced effect was obtained in the experiments with synchronized cultures, when exposed to Ft in the S-phase of the cell cycle.