Benomal, a systemic fungicide, was administered to male Sprague-Dawley rats during the prepubertal, pubertal, or postpubertal stage of reproductive development. Animals received 5 or 10 daily treatments of 0, 125, 200, 250, 500, or 1000 mg benomyl/kg-d by gavage. Observations were made at selected intervals after exposure and included hemotological parameters, body weight, tissue weights, total epididymal sperm counts, vas deferens sperm concentrations, serum follicle-stimulating hormone (sFSH) levels, and testicular histology. Data presented here suggest that there is an age-related difference in sensitivity to benomal.