Toluene is a widely abused inhaled solvent. This study was designed to determine whether toluene abuse affects the reproductive functions or general health of males. Seven-week-old male Sprague-Dawley rats were exposed to toluene vapor inhalation (0, 4000, or 6000 ppm; 2 h/day) daily for 5 weeks. Exposure-related suppression of body weight gain and food consumption were observed. Salivation and lacrimation were observed during exposure periods and intensified with repeated exposure. Rats exposed to 6000 ppm toluene had decreased spleen and thymus weights, as well as suppressed lymphocyte counts. In 6000 ppm group, the epididymal sperm counts, sperm motility, sperm quality and in vitro penetrating ability to zona-free hamster eggs were significantly reduced, while no exposure-related changes in the testes weight or spermatogenesis within testes were detected. Tail-less sperm heads were seen within zona-free eggs incubated with sperm from rats exposed to 6000 ppm toluene, but not control rats. No significant changes were observed in serum luteinizing hormone, follicle-stimulating hormone, or testosterone levels following 1 month of exposure to 6000 ppm toluene. These results indicate that high concentrations of toluene may directly target sperm in the epididymis and disrupt sperm maturation.