PURPOSE: Evaluate the histological changes in parenchyma´s epithelial layer of the uterus and ovarian of rats with induced endometriosis, treated with Uncaria tomentosa extract. METHODS: 29 rats with experimental endometriosis, were selected and divided in three groups: The uncaria group received 32mg/ml of Uncaria tomentosa extract, 1ml administered daily and the placebo group received 1ml of saline 0.9% per day, during for 14 days (both groups); the leuprolide group received leuprolide acetate 1mg/kg body weight applied single subcutaneous dose. In the 15th day of treatment the uterine horn and ovaries were removed for histopathological analysis. RESULTS: The uncaria group presented nine samples (90%) with immature ovarian follicles, whereas the placebo group did not present any case and in the leuprolide group there were eight rats (88%) with the same change. The placebo group showed mature corpus luteum in all animals, occurring less frequent in uncaria (10%) and leuprolide (22%) groups. The uterine epithelium showed weak proliferative in nine (90%) samples of the uncaria group, in two (20%) animals in the placebo group and seven (77.8%) rats in the leuprolide group. CONCLUSIONS: The findings suggest that Uncaria tomentosa has contraceptive effect.