. (1973). Thorax, 529-532. Saccular aneurysm caused by bacterial endocarditis in a syphilitic aorta. The rapid development of a saccular aneurysm during successfully treated bacterial endocarditis, in an ascending aorta previously affected by syphilis which had been treated with adequate chemotherapy 15 years previously, is described. Although bacterial endocarditis does occasionally complicate syphilitic aortic valve disease, the literature does not contain any report of resulting aneurysm development. The investigation and successful surgical treatment of the case are described.The development of saccular aneurysm of the thoracic aorta following syphilitic infection has long been recognized and Kampmeier (1938) found that 93 % of aneurysms in this site were of luetic origin. More recent surveys by Roberts, Danielson, and Blakemore (1957) and Carlsson and Sternby (1964) showed that the proportion decreased to 50% and 26% respectively. In these and other reports of large clinical and pathological studies concerning cardiovascular syphilis (Colt,