To study the frequencies of numerical and structural aberrations for chromosome in sperm of benzene exposed workers, the multi-color FISH was used. Four DNA probes(one for chromosome 1 centromere and one for 1 p terminal, and two for chromosome 18 centromere) were hybridized with interphase sperms, and the frequencies of numerical aberrations for chromosome 1, 18 and structural aberrations of chromosome 1 were detected simultaneously. The time weighted average concentration (TWA) of benzene in workplace (42.29 mg/m3) was higher than that of our national maximum allowable concentration (6 mg/m3). The geometric concentration of urinary trans, trans-muconic acid(tt-MA) in exposed group was significantly higher than that of control group. A total of 144,282 sperm of 15 benzene-exposed workers and 135,937 sperm in 14 controls were scored. The frequency of hybridization efficiency was 99.85%. The mean frequencies of disomic sperms for chromosome 1 and 18 in exposed group(0.088% +/- 0.041%, and 0.087% +/- 0.049%, respectively) were statistically increased over that of the control group(0.045% +/- 0.024%, and 0.035% +/- 0.028%), and the mean frequencies of nullisomic sperms for chromosome 1 and 18(0.11% +/- 0.059%, 0.075% +/- 0.035%) in exposed group were statistically increased over that of control group too (0.048% +/- 0.018%; 0.045% +/- 0.024%). The frequencies of diploidy sperm were no difference in both exposed and control groups. The mean frequencies of terminal duplication and terminal deletion for chromosome 1 p(0.16% +/- 0.037%; 0.14% +/- 0.053%, respectively) were significantly increased over that of control group(0.082% +/- 0.023%; 0.069% +/- 0.028%, respectively). The mean frequencies of centromeric duplication and centromeric deletion for chromosome 1(0.10% +/- 0.035%; 0.10% +/- 0.041%, respectively) were significantly increased over that of control group(0.075% +/- 0.023%; 0.060% +/- 0.029%). Our experiments showed that exposed to benzene at higher concentration(42.29 mg/m3) may induce increases in frequencies not only of numerical aberrations for chromosome 1 and 18, but also of structural aberrations for chromosome 1 of sperms in exposed workers.