The aim of this work is to analyse chromosome aberrations and cell cycle kinetics in workers occupationally exposed to organic solvents, which contain benzene among other agents. In the exposed group structural chromosome aberrations were found in 2%, while in the control group in 0.9% of analysed metaphases. Detailed band localization of breakpoints in chromosomes of patients in both groups is presented. No significant differences in cell cycle kinetics in individual members of exposed and control groups were found.