Objective: To examine the pro-resolution actions of 15-epi-lipoxin A(4) (LXA(4)) on endometriotic lesions, on the concentrations and activities of matrix metalloproteinases (MMP-2 and MMP-9) in murine endometriosis. Design: Prospective, vehicle-controlled experimental study. Setting: Animal research facility. Animal(s): BALB/c mice. Intervention(s): Endometriosis (EM) was induced in 30 mice. Fifteen of them were administered LXA(4) for 24 days (LXA(4) group), whereas the other 15 served as a control group (EM group). Another 15 sham-operated mice (sham-operated group) were treated with vehicles. Main Outcome Measure(s): The weight of the endometriotic lesions was measured. The concentrations, mRNA, and activities of MMP-2 and MMP-9 were determined by enzyme-linked immunosorbent assay, quantitative real-time polymerase chain reaction, and gelatin zymography, respectively. Result(s): Compared with EM group, the weight of the endometriotic lesions was decreased, the concentrations of MMP-2 and MMP-9 dropped, the mRNA levels of MMP-2 and MMP-9 in the peritoneal fluid cells and the endometriotic lesions were reduced, and the activities of MMP-2 and MMP-9 were inhibited in the LXA(4) group. Conclusion(s): LXA(4) may inhibit the progression of endometriosis possibly by lowering the concentrations and the activities of MMP-2 and MMP-9. (Fertil Steril (R) 2010;93:1440-7. (C)2010 by American Society for Reproductive Medicine.)