The aim of this study was to examine whether an association exists between glutathione S-transferase Mu-1 (GSTM1) gene polymorphism and idiopathic male infertility. Forty-two men with infertility and 43 fertile men were recruited for this study. GSTM1 gene was analysed using PCR technique. The frequency of GSTM1 null (-) genotype was observed to be 45.2% in infertile men as against 20.09% in fertile men. Subjects with the GSTM1 null genotype had lower sperm concentrations and motility when compared with the subjects with GSTM1-positive genotype in both the groups. This study shows that the frequency of GSTM1 null (-) genotype is significantly high in infertile males when compared with the frequency in fertile males (OR = 0.32, P = 0.017, 95% CI = 0.124-0.831).