The purpose of this study was to consider the cause of the prolonged inflammatory reaction that sometimes appears after endovascular stent-graft repair for dissecting aortic aneurysm. Endovascular stent-grafting was performed in 12 patients (11 men and 1 woman, mean age 60±9.8). Endovascular stent-grafting was indicated to close the entry of type B dissections in 10 patients and to exclude ulcer-like projections (ULP) in 2 patients. On the 7th postoperative day (POD), aortography showed no endoleak in 7 type B cases (A-group), remaining endoleak in 3 type B cases (B-group), and complete exclusion in 2 ULP cases (C-group). The value of FDP-E in the A-group was high on the first POD and then decreased gradually. FDP-E also increased up to the 7th POD in the B-group, and increased very slightly after the operation in the C-group. The values of WBC and CRP increased up to the 3rd POD in all groups, but in the A-group it was still high on the 7th POD. On contrast-enhanced CT performed after the procedure and on the 7th POD, edema (over 10mm in thickness) around the descending thoracic aorta was demonstrated in 5 out of 7 cases in the A-group, but in none of the cases in the B- and C-groups. A segmental atelectasis in the left lung was detected in 6 out of 7 cases in the A-group, but in none of the cases in the Band C-groups. In the A-group, endovascular stent-grafting influenced thrombus formation, and the thickened edema around the descending thoracic aorta and the atelectasis produced in the left lung were prominent more than in the other groups. These results suggest that the Inflammation around aortic wall induced by thrombosis in the false lumen, might contribute to the development of the edema around the descending thoracic aorta and the atelectasis in the left lung. We conclude that the inflammatory reaction might have prolonged the postoperative course in the A-group patients.