In this study, we investigated the effects of polychlorinated biphenyls (PCBs) and organochlorinated pesticides on the serum levels of luteinising hormone (LH), follicle stimulating hormone (FSH) and weights and histomorphometry of uterine tissue in immature female rats using uterotrophic assay. A total of 36 rats were randomly divided into six groups (n = 6 per group) as control, oestradiol (E-2, 100 mu g/kg), PCB 180, Aroclor 1221, endosulfan and mirex at 10 mg/kg dosage. After 3 days of injections (subcutaneous), animals were decapitated and blood samples were collected. Uteri were dissected, weighed out and then fixed in 10% formaldehyde. They were processed for histomorphometry. The serum levels of LH and FSH were determined by enzyme immunoassay.