Objective: To examine the effect of somatostatin analogs on surgically induced endometriosis in rat models. Study design: Endometrial tissue was implanted onto the abdominal peritoneum of 26 rats that were randomized into 3 groups. The rats in group 1(n = 9) were subcutaneously administered with 0.02 mg/kg/d of octreotide (a short-acting analog) for 28 days. The rats in group 2 (n = 8) were subcutaneously injected with 20 mg/kg of a single dose of a long-acting analogue lanreotide The rats in group 3 were given no medication and served as controls (n = 9). Results: Mean volume and histologic score of implants in groups 1 (P < .01 and P < .05, respectively) and 2 (P < .01 and P < .05, respectively) were significantly lower than that in group 3. There were significant reductions in vascular endothelial growth factor (VEGF) and matrix metalloproteinase 9 (MMP-9) immunoreactivities in group 1 (0.67 +/- 0.50 and 1.22 +/- 0.44, respectively; both P < .01) and group 2 (0.71 +/- 0.48 and 0.86 +/- 0.69, respectively; both P < .01) when compared with the control group (1.78 +/- 0.83 and 2.11 +/- 0.78, respectively). Conclusion: Somatostatin analogs has regressed significantly the size of the endometriotic implants and caused atrophy of these lesions in rats by decreasing explant levels of VEGF and MMP-9.