In the past thirty years, fifty arterial aneurysms due to non-specific inflammation in forty-two patients were operated on. Twenty-five patients were males and 17 were females; their average age was 38 years. The majority of the aneurysms were located in the abdominal aorta, common carotid artery, and femoral artery. Clinical diagnoses were Takayasu's disease (11), Behçet's disease (3), giant cell aortitis (2), and systemic lupus erythematosus (1). The other twenty-five cases were of undetermined etiology. There were fourteen cases of rupture, and long-term steroid administration in five cases was suspected of playing a major role in inducing this grave sequel. Aneurysmectomy with arterial reconstruction was performed on 37 cases. Various histological findings of inflammation were observed in the resected specimens. The suture aneurysms occurred in eight cases in the late period. Surgical care of non-specific inflammatory arterial aneurysms was judged to be more difficult than that of atherosclerotic aneurysms.