Abstract: Objective To observe the toxic effect of 90 days' di-(2-ethylhexyl)phthalate (DEHP) exposure on motility of rat sperm.Methods Forty male Sprague-Dawley (SD) rats of clean grade were randomly divided into a control and a DEHP exposure group.The rats of the exposure group were treated with DEHP at the doses of 5,50 and 500 mg/kg orally for 90 days continuously.Testis and epididymis of all the rats were weighed and then the epididymis was collected with ‘diffusion’ method by the end of the treatment.Effects of DEHP on the motility of isolated sperms were analyzed with computer assisted sperm analysis (CASA) system.Results The percentage linearity(LIN)of the sperms of rats exposed to 5 mg/kg DEHP was significantly lower that those of the control rats (44.00±2.52% vs.50.00±2.71%,P<0.05).The beat cross frequency(BCF) of the sperms of rats exposed to 500 mg/kg DEHP was significantly lower that that of the control rats (5.8±4.2 Hz vs.10.4±1.7 Hz,P<0.05).All the motility parameters of sperms of the rats treated with 500 mg/kg DEHP reduced significantly compared with those of the controls (P< 0.05 or P< 0.01).With the increase of DEHP concentration,the parameters of sperm motility decreased.Conclusion The results demonstrate that DEHP exposure could result in direct toxic effects on motility of sperms in caudal epididymides of rats.