Objective: To determine the effects of oxytocin (OT) on surgically induced endometriosis in a rat model. Study design: Twelve female Sprague-Dawley rats were included. After the implantation and establishment of autologous endometrium onto the abdominal wall peritoneum, the rats were randomly divided into two groups, treated with intramuscular oxytocin (OT group, 160 mu g kg/day, n = 6) or isotonic NaCl solution (control group, 1 mL kg/day, n = 6) for 28 days. To evaluate the therapeutic effects of OT, the explant volumes were calculated and the levels of vascular endothelial growth factor (VEGF), monocyte chemotactic protein-1, and TNF-alpha were measured in plasma and peritoneal fluid. Endometriotic explants were examined histologically by semiquantitative analysis.