The present study aimed to investigate the effect of synthetic pyrethroid (katron) and fluoride on the reproductive activities of male albino rats. One hundred and twentyapparently healthy immature male albino rats with initial weigh 20-30 grams and 30 days old were divided into four groups (30 rat /group), group I remained untreated and served as negative control group, group II were received Katron (pyrethroid insecticide) in doses of 1/10 of LD50 (8 mg/kg, b.wt.) orally by using stomach gavage day after day along the period of experiment (for 12 weeks), group III were administered sodium fluoride (NaF) in drinking water in a dose of 150 mg/Liter, group IV were received both Katron and sodium fluoride in the same doses and manner as in group II and III. Complete sperm picture, testosterone concentration, lipid peroxide levels and superoxide dismutase activity in serum, also testosterone concentration, lipid peroxide levels and glutathione reduced activity in testicular homogenate and histopathological changes in testes were examined to evaluate the reproductive efficiency of the treated male rat.  Significant decrease in sperm motility%, sperm cell concentration, live sperm%, serum testosterone concentration, and serum superoxide dismutase activity were recorded. Also, decrease in testicular concentration of testosterone and glutathione reduced activity and significant increase in total sperm abnormalities percentage and lipid peroxide levels in both serum and testicular homogenate were noticed. All the pervious changes are seen in the all treated groups but they are marked and obvious in the fourth group (treated with both katron and sodium fluoride). In conclusion there are an obvious toxic interaction between pyrethroid and fluoride on the reproductive efficiency of the treated male rats especially when the exposure begin in young ages before maturity.