To investigate the toxic effect of terephthalic acid(TPA)on testicular functions of rats, male Sprague-Dawley rats were orally administered TPA in diet at the levels 0(control),0.2,1 and 5%for 90 days.Testicular functions were assessed by histopathology,testicular sperm head counts,daily sperm production, sperm motility (measured by computer-assisted sperm analysis, CASA), biochemical indices(marker testicular enzymes), and serum testosterone.Oral feeding with terephthalic acid did not cause body and testes weight loss in TPA-treated groups.Histopathologically,damages of spermatogenic cells and Sertoli cells were observed by electron microscope,testicular sperm head counts, daily sperm production,and activities of sorbitol dehydrogenase (SDH) were decreased significantly in the 5% TPA group.The motility of spermatozoa was reduced significantly in all treated groups,which was correlated with administration doses. Serum testosterone concentrations were not declined in treated groups.In conclusion,TPA can cause impairment of testicular functions.The primary sites of action may be spermatogenic cells and Sertoli cells.The results of the present study provide first information of TPA on testicular functions in male rats.