Purpose of investigation: To evaluate the preventive and reducing effect of aloe vera gel on surgically-induced endometrial foci in rats. Materials and Methods: Twenty-four reproductive aged female non-pregnant, nulligravid Sprague-Dawley albino rats were used. The rats were randomly divided to three groups (Group 1: control, Group 2: aloe vera endometriosis formation, and Group 3: aloe vera endometriosis treatment). A peritoneal lavage using one-ml saline was taken at all the operations for determination of superoxide dismutase (SOD), malondialdehyde (MDA), and catalase (CAT). Forty-eight horns were implanted in 24 rats. Results: All the implants were properly formed after implantation. In Group 3, before aloe vera application, the sum of the volumes was 87.2 ± 20.4 mm³ and after treatment the volumes dropped to 28.9 ± 14.9 mm³ (p = 0.01). As evaluation of aloe vera on the formation of endometriosis in the second operation in Group 2, the sum of the volumes was 2.9±1.4 mm³ and in Group 1, 118.9 ± 20.0 mm³(p = 0.001). Likewise, similar changes were observed in the histopatological scores. Conclusion: The application of aloe vera was seen to raise antioxidant levels in the peritoneal fluid and to reduce oxidative stress markers. Aloe vera is effective in the inhibition of formation and regression of endometriotic lesions.