Abstract： Background Chromosomal aberrations are the major cause of pre-and post-implantation embryo wastage and some studies suggest that half of all human conceptions have a chromosomal abnormality. A chromosomal aberration in human sperms is also one of the causes of failure of in vitro fertilization. This study was designed to ascertain whether chromosomal aneuploidy in spermatozoa is a risk factor for male infertility.Methods Twelve infertile men were divided into two groups: 10 with oligoasthenoteratozoospermia (OAT, Group A) and two with a normal semen analysis (Group B). Two normal healthy sperm donors acted as controls (Group C). We used fluorescence in situ hybridization (FISH) and probes for chromosomes X, Y and 18 to determine the frequency of aneuploidy.Results The frequencies of spermatozoa disomy for chromosomes X, Y and 18 were 0.30% and 0.30%, respectively, in Group B. The percentages were not significantly different from those of Group C (0.15% and 0. 16%). The frequencies of nullisomy for chromosomes X, Y and 18 were 0.15%and 0 for Group B, and 0 and 0.15% for Group C (P＞0.05). In Group A, the incidences of disomy were 1.13% and 0. 96% and the frequencies of nullisomy were 1.13% and 1.60%. In these three groups, the incidences of diploidy were 0.60%, 1.00%, and 0.30%, respectively. Both the frequencies of disomic and nullisomic spermatozoa for chromosomes X, Y, and 18 and of diploid spermatozoa were significantly higher in Group A than in Groups B and C. The estimated total aneuploidy rates in the sperm from the three groups were 42.44%, 6.05%, and 2.59%,respectively.Conclusion These results indicate that chromosomal aneuploidy in spermatozoa may be a risk factor for infertility.