Oral administration of di(2-ethylhexyl)phthalate (DEHP) in doses of 250, 500, 1000 and 2000 mg/kg to adult rats for 15 days caused a significant dose dependent decrease in the sperm count of the epididymal spermatozoa. The activity of gamma-glutamyl transpeptidase (gamma GT) and lactate dehydrogenase (LDH) was significantly increased in the animals of the treated groups. An increase in the activity of beta-glucuronidase and decrease in the activity of acid phosphatase was also observed at the highest dose of DEHP. The activity of sorbitol dehydrogenase (SDH) was found to be decreased in the animals exposed to 1000 and 2000 mg/kg of DEHP. These results suggest that DEHP can affect spermatogenesis by altering the activities of the enzymes responsible for the maturation of sperms. The reduced number of sperms may be responsible for the antifertilic effects of DEHP.