Cytosolic glutathione S transferases are a family of related isozymes that catalyze the conjugation of reduced glutathione to a wide range of electrophilic substrates, including ROS and carcinogenic compounds and their metabolites. GST expressed in human tissue, comprise the alpha (A), mu (M), pi (P), theta (T), kappa (K), omega (O) and zeta (Z) gene families. Among these classes of GST, GST-M1, GSTM3, GST-T1, GST-P1 and GST-Z1 have been shown to be polymorphically distributed. It has been postulated that human semen contains a significant amount of glutathione S- transferase (GST) and that the enzyme could attenuate the toxicity of ROS to sperm. However, few reports have investigated the relationship between GST genotypes and sperm damage caused by oxidative stress among infertile men with Vx.