SUMMARY THE EFFECTS OF DIETHYLSTILBESTROL ON EPIPHYSEAL PLATES IN THE RATS In order to investigate the effects of prenatal diethylstilbestrol (DES) administration on epiphyseal plates, 5 U g/day DES injected subcutaneously to 8 female and 8 male rats for 5 days beginning the day of birth. The other 8 female and 8 male rats were followed to be control group. At the and of the 3 th month, the widenings of the lower femoral and upper tibial epiphyseal plates were measured and histological changes were evaluated. In histologic examinations, the cartilage proliferation in epiphyseal plates were found to be decreased and the cartilage maturation and calcification were found to be increased in DES injected group. There were significant narrowing, in the measurements of the epiphyseal plate widenings, in the DES injected rats (p