Peripheral blood lymphocyte 8-hydroxy-2-deoxyguanosine (8-OHdG), were detected in 87 benzene-exposed and 30 control subjects by high performance liquid chromatograph coupled with an electrochemical detector system (HPLC-EC). The air concentration of benzene and its homologes in the workplace, urinary trans,trans-muconic acid (TTMA) as an internal dose of benzene exposure, were examined. The lymphocyte micronuclei (MN) as genotoxic and white blood cell (WBC) count as well as the myelotoxic markers of benzene were examined. Exposure to low, medium and high concentrations of benzene resulted in increased levels of 8-OHdG, which were 4.67, 26.12 and 29.89/10(5) dG, respectively, However, the 8-OHdG level observed in the control group was 3.738/10(5) dG). A good correlation between 8-OHdG formation and the groups exposed to external and internal benzene was observed (r = 0.77, 0.64, respectively). There was also a correlation between 8-OHdG and MN formation (r = 0.50). WBC levels were within normal range in all benzene-exposed subjects. It may be concluded that: benzene induced DNA oxidative damage in occupational exposure workers. The major factors influencing blood the 8-OHdG level were sex and toluene.