Microbial infections, localized as well as systemic, are known to cause transitive or permanent male infertility. However, the mechanisms of infection-induced infertility are largely unknown. Earlier reports showed that steroidogenesis and spermatogenesis are affected during bacterial lipopolysaccharide (LPS)-induced acute inflammation. The present study used an LPS rat model to investigate the role of oxidative stress in spermatogenesis. Intraperitoneal administration of bacterial LPS (5mg/kg body weight) to adult male albino rats elevated testicular malondialdehyde (MDA) and 4-hydroxy-2-nonenal (HNE), and decreased the activities of testicular antioxidant enzymes such as catalase, superoxide dismutase, glutathione peroxidase, and glutathione reductase. The GSH/GSSG ratio also decreased significantly. Time series analysis revealed transitory oxidative stress and expression of inflammatory mediators such as interleukin-1beta (IL-1beta), inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) from 3h to 12h after LPS. Testicular expression of steroidogenic acute regulatory (StAR) protein decreased to 24h, in correlation with damage to spermatogenesis. These data are consistent with oxidative stress as a major causal factor in altered steroidogenesis, spermatogenesis, and perhaps male infertility during endotoxin-induced acute inflammation.