Varicocele is one of the leading causes of male infertility, and is present in almost 40% of infertile males. Recent understanding of the role of oxidative stress in male reproduction has led some researchers to postulate oxidative stress as the possible cause of sperm dysfunction in varicocele patients. The objective of the present study was to examine the published literature on the role of oxidative stress in patients with varicocele as the aetiology of their infertility. Twenty-three human studies were identified after an extensive search dealing with the role of oxidative stress in varicocele-associated infertility. Out of these studies, four were selected that measured similar types of reactive oxygen species (ROS) by a similar method of measurement. The data were then entered in the RevMan software for analysis. The overall estimate showed that patients have significantly higher concentrations of ROS than controls, with the mean difference being 0.73 (95% CI 0.40, 1.06, P < 0.0001). This translated to an ROS concentration of 4.37 x 10(4) cpm/20 x 10(6) spermatozoa/ml on the linear scale. Total antioxidant capacity levels were found to be significantly lower in the infertile varicocele patients, with 386 fewer trolox equivalents than the controls (95% CI -556.56-216.96, P < 0.00001). From the results, it can be concluded that there is increased oxidative stress in varicocele patients; however, more studies are needed to confirm this finding.