Review of 91 confirmed cases of thoracic aortic dissection revealed that the findings on the plain films of the chest often were suggestive of the diagnosis, with abnormalities in the aortic countour, especially when comparison was made with previous roentgenograms. The diagnosis was definitively made in 52 cases by retrograde transfemoral or transaxillary catheterization accomplished without complication. The most common angiographic findings were opacification of the false lumen, visualization of an intimal flap, and deformity of the true lumen. Early diagnosis and institution of appropriate therapy can improve survival in this disease.