Objective To assess the effect of benzene on sperm DNA damageMethods Twenty-seven benzene-exposed workers were selected as exposed groupand 35 normal sperm donors as control group. Air concentration of benzene series inworkshop was determined by gas chromatography. As an internal exposure dose ofbenzene, the concentration of trans, trans-muconic acid (ttMA) was determined byhigh performance liquid chromatography. DNA was detected by modified single cellgel electrophoresis (SCGE).Results The air concentrations of benzene, toluene and xylene at the workplace were86.49 ± 2.83 mg/m3, 97.20 ± 3.52 mg/m3 and 97.45 ± 2.10 mg/m3, respectively.Urinary ttMA in exposed group (1.040 ± 0.617 mg/L) was significantly higher thanthat of control group (0.819 ± 0.157 mg/L). The percentage of head DNA, determinedby modified SCGE method, significantly decreased in the exposed group (n=13, 70.18%± 7.36%) compared with the control (n=16, 90.62% ± 2.94%)( P<0.001).Conclusion The modified SCGE method can be used to investigate the damage ofsperm DNA. As genotoxin and reprotoxins, benzene had direct effect on the germ cellsduring the spermatogenesiss. Objective To assess the effect of benzene on sperm DNA damage Methods Twenty-seven benzene-exposed workers were selected as exposed group and 35 normal sperm donors as control group. Air concentration of benzene series in workshop was determined by gas chromatography. As an internal exposure dose ofbenzene, The concentration of trans, trans-muconic acid (ttMA) was determined by high performance liquid chromatography. DNA was detected by modified single cellgel electrophoresis (SCGE). Results The air concentrations of benzene, toluene and xylene at the workplace were 86.49 ± 2.83 mg / m3, 97.20 ± 3.52 mg / m3 and 97.45 ± 2.10 mg / m3, respectively.Urinary ttMA in exposed group (1.040 ± 0.617 mg / L) was significantly higher thanthat of control group (0.819 ± 0.157 mg / L) of head DNA, determined by modified SCGE method, significantly decreased in the exposed group (n = 13, 70.18% ± 7.36%) compared with the control (n = 16, 90.62% ± 2.94% SCGE method c an be used to investigate the damage ofsperm DNA. As genotoxin and reprotoxins, benzene had direct effect on the germ cellsduring the spermatogenesiss.