We investigated age-specific mortality rates of 836 patients with ankylosing spondylitis diagnosed during 1935-57. These patients were not given deep x-ray therapy, and thus their mortality was not confounded by possible late effects of radiation. Follow-up observation was to January 1, 1968--on the average, over 13 years from enrollment. Men had higher mortality than women; excess mortality was observed in men for diseases known to be associated with spondylitis, such as ulcerative colitis, nephritis and tuberculosis or other respiratory disease. In addition, their mortality risk relative to the general male population was fourfold for all gastrointestinal disease, nearly twofold for accidents, suicide and cerebrovascular disease and 40 per cent in excess for other circulatory diseases. These results indicate that, at least in men, ankylosing spondylitis has life-threatening consequences related to many organ systems, consistent with systemic vascular degeneration as one long-term consequence of the disease.