This study systematically investigated the effects of fluoride ion (F)exposure on the male reproductive organ and on spermatogenesis. Twenty male rats were divided into two groups of 10 and treated with 0 or 150 mg F/L in drinking water. After 70 days, the body weight, organ coefficients of the testis and epididymis, sexhormone levels in serum, and sperm quality were measured. The histology of the testis and epididymis was observed via light microscopy, and the ultrastructure of the epididymis and sperm was studied via transmission electron microscopy. Fluoride treatment significantly decreased (p<0.01) the body weight and organ coefficients, as well as seriously damaging the histological structure of the testis and epididymis of the rats. The fluoride-exposed rats exhibited obvious ultrastructural changes of the spermand epididymis, such as shedding sperm heads and acrosome, as well as mitochondrial swelling and vacuolization. In addition, fluoride treatment significantly decreased the serum levels of sex hormones, including testosterone, luteinizing hormone andestradiol (p<0.01) while also decreasing the serum level of follicle-stimulating hormone(p<0.05). Furthermore, fluoride treatment significantly decreased sperm density and motility (p<0.01), and significantly increased the rate of teratospermia (p<0.01). These results indicate that fluoride exerts toxic effects on the testis and epididymis by decreasing the organ coefficients of the testis and epididymis, damaging the structure of the testis and epididymis, disturbing the secretion of sex hormones, and affecting sperm quality, with the ultimate result of diminishing sperm function.