Behçet's disease associated with large vascular lesions is called vasculo-Behçet's disease. The pathologic features of eight autopsy cases of vasculo-Behçet's disease were studied. The patients' ages ranged from 31 to 56 years; there were five men and three women. Of these patients, large vascular lesions were as follows: aneurysm (three cases), aneurysm and arterial occlusion (one case), aneurysm with arterial and venous occlusion (one case), and venous occlusion (two cases). Aneurysms were of the saccular or dissecting type. The aneurysm formation most commonly occurred in the aorta (two cases). Histologically, aortitis was seen in six patients. Aortitis was divided into active and scar stages. In one case with active stage aortitis, granulomatous aortitis similar to Takayasu's arteritis was seen. In conclusion, we believe that the large arterial lesion in vasculo-Behçet's disease represents inflammation occurring in the media and adventitia. In the affected arteries, active arteritis occurs initially, followed by destruction of the media and fibrosis. Saccular aneurysms are probably produced by severe destruction of the media by intense active inflammation. The large venous lesions represent thrombophlebitis.