A spiral CT scan was performed at 6 months to detect presence of endoleaks. MMP-3 and MMP-9 levels were measured before EVG (nϭ30) and OSR (nϭ15) treatments and at 1, 3, and 6 months of follow-up by a sandwich ELISA technique. Healthy volunteers (nϭ10) were used as control subjects. Immunohistochemical staining for MMP-9 and MMP-3 was performed on tissue samples from surgical cases. Both MMP-9 and MMP-3 mean basal levels were significantly higher in patients affected by AAA than in control subjects (32.3Ϯ20.7 ng/mL for EVG and 28Ϯ9.9 ng/mL for OSR versus 8.9Ϯ2.5 ng/mL, 2PϽ0.05; 18.3Ϯ9.7 ng/mL and 26.7Ϯ10.8 ng/mL versus 8.2Ϯ5.3 ng/mL, 2PϽ0.001).In the OSR group, both MMP-9 and MMP-3 mean levels decreased after surgery (28Ϯ9.9 ng/mL at basal versus 14.7Ϯ6.6 ng/mL at 6 months, 2PϽ0.001; 26.7Ϯ10.8 versus 12Ϯ5.3 ng/mL; 2PϽ0.001). In the EVG group, a statistically significant difference at 6-month follow-up in MMP-9 and MMP-3 mean plasma values was detected in patients who had endoleakage in comparison with patients without endoleakage (44.3Ϯ20.7 versus 14.6Ϯ7.0 ng/mL, 2PϽ0.005; 25Ϯ11.5 versus 10.3Ϯ5.4 ng/mL, 2PϽ0.005). Conclusions-After EVG exclusion, MMP-9 and MMP-3 levels decreased to a level similar to that of patients undergoing OSR. In addition, a lack of decrease in MMP levels after EVG exclusion may help in identifying patients who will have endoleakage and consequent aneurysm expansion caused by continuous sac pressurization during follow-up.