A 31-year-old man with bacterial endocarditis developed a mycotic popliteal aneurysm which presented clinically like an acute osteomyelitis. Bone and Ga-67 scanning played a major role in disclosing this unsuspected lesion. Various isotopic techniques proposed for the detection of mycotic aneurysm are reviewed. The potential usefulness of Ga-67 imaging in patients at risk of developing such lesions is discussed.