Sodium fluoride (NaF) administered orally to adult male rats at a dose level of 4.5 ppm and 9.0 ppm for 75 days caused significant decrease in the body weight, brain index and testicular index. A significant decrease in sperm count, sperm motility, sperm viability and sperm function (HOS positive) with increased sperm abnormalities was also observed in NaF-exposed male rats. The activity levels of testicular steroidogenic marker enzymes 3β-hydroxysteroid dehydrogenase (3β-HSD) and 17β-hydroxysteroid dehydrogenase (17β-HSD) were significantly decreased in NaF-treated rats indicating decreased steroidogenesis and in turn spermatogenesis in rats exposed to NaF.