The majority of cases involving clinically significant aortitis result from Takayasu's disease, syphilis, and mycotic aneurysms, although aortitis may occur as a part of the clinical manifestation in other diseases of known and unknown etiology. Syphilitic aortitis can be treated successfully if an accurate diagnosis is made early and if appropriate antibiotic therapy is instituted. Untreated or treated inadequately, late cardiovascular complications can occur, namely, aortic aneurysm, aortic valvular insufficiency and coronary osteal stenosis. Surgical treatment should be considered when any of these late complications become manifest. Aortitis can occur with rheumatic fever and, occasionally, in rheumatoid arthritis. Giant-cell arteritis is a disease that can affect large, medium or small arteries, and usually occurs in patients over 50 years of age, chiefly women. The entire aorta may be affected. It is the only form of aortitis commonly associated with dissecting aneurysm of the aorta. Corticosteroids are effective in treating the active form of the disease and can usually prevent the development of later severe complications. Surgery is indicated when a dissecting aneurysm develops.