Abstract: Bis-trichloromethyl sulfone(BTS) given po to male Sprague-Dawley rats at a dose of 10 mg·kg^-1·d^-1, 6 days a week for 8 weeks(or 30 mg·kg^-1·d^-1 for 4 weeks), was found to lead to infertility. The density and, in particular, the motility of the spermatozoa in the cauda epididymidis were significantly lower than those of the controls (P<0.001). The body weight, the sex behavior, the blood testosterone level and the histology of important organs were not significantly different from those of the control rats. Fertility started to recover 4 weeks after cessation of medication and was entirely recovered 2 more weeks later in rats having received BTS for 8 weeks at the dose of 30 mg·kg^-1·d^-1. In vitro study showed that BTS at a concentration of 0.31 mg·ml^-1 would make rat spermatozoa immobile within 20 seconds. These results indicate that BTS has both antifertility effect in male rats and direct inhibitory effect on rat spermatozoa. We conclude that nontoxic doses of BTS can induce reversible infertility in male rats.