Abstract: The results of the preliminary observation on antifertility pharmacodynamics of tripchlorolide （T4） in male rhesus monkeys and reversibility of fertility after cessation of the treatment was reported. Twelve sexually mature male rhesus monkeys were randomly divided into 4 groups. T4 was adminstered orally at daily doses of 50, 25，10，0 μg/kg,6 times a week，for 8 consecutive weeks. Necrospermia，azoospermia or severe oligozoospermia（＜1×10⁶/ml) was ob-serueed at the end of 8th，7th and 5th week of treatment in the treated groups respectively. Bending of midpiece and separation of the head and tail were found in the silver stained preparations of ejaculated spermatozoa after treatment, however, sperm head morphology was still almost normal. During the T4- treatment period, there were no significant differences in the spontaneous ejaculatory frequency，electroejaculatory response, ejaculate weights, testicular volume，serum testosterone levels and seminal fructose concentration in treated groups as compared with the control. However,the carnitine content of seminal plasma changed nonuniformly in T4-treated animals. Sperm density and viability were restored to normal levels at 10th, 8th，and 4th week after cessation of treatment in 3 treated groups respectively.The finding on reversibility of fertility was confirmed by mating test. The results showed that Tripchlorolide possesses reversible antifertirity effect in male rhesus monkeys at the tested doses.

Key words: Tripchlorolide, Male, Rhesus monkey, Antifertirity, Reversibility of fertility