Most of chemical drugs have side effects on various parts of body. It is necessary to identify these effects to better use of drugs. Dexamethasone is one of the most usual steroidal anti-inflammatory drug in animal medication. The long term effect of this drug on male reproductive of mice was the goal of this study. Fifty matured male mice were divided into five groups including control, placebo and three treatment groups. Placebo group was received physiological serum only which were injected in peritoneum every other day and for twenty days. After 20 days, reproductive parameters, including testes weight, testicular germ cells and early spermatocytes, epididymal sperm count, reproductive hormones, including FSH, LH and testosterone and fertility rate were measured. The results showed that testis weight, testicular germ-cell level, primary spermatocytes, epididymal sperm and fertility in rats at all doses of dexamethasone significantly decreased. FSH levels increased in the treated group, LH decrease in 0.1 group  but in treatment 1 had a significant increase . Testosterone in dose of 1 mg/kg significantly increased compared with the control group.

So, mentioned drugs are effective on reproductive action of reproductive system dose dependently and probable effect of them must be considered in time of using.