Mycotic aneurysms not associated with trauma or atherosclerosis are uncommon. Their clinical presentation is insidious and lacks definite diagnostic criteria. This retrospective study of 14 patients treated over a period of 9 years confirms this, and shows that half are associated with a predisposing infected focus and that the main presenting clinical feature is that of a painful mass (64%) which is often mistaken for some other diagnosis. The main extracranial, extrathoracic site of predilection was the iliofemoral segment (65%). The main diagnostic investigation was angiography, which was also used to uncover silent aneurysms elsewhere in the arterial tree. Urgent surgical treatment is mandatory since complications may occur at any time and these may include life-threatening bleeding. Two of our patients experienced life-threatening gastro-intestinal bleeding while in hospital. The mainstay of treatment was surgical resection and reconstruction using an autologous vein or artery if possible. The more serious complication of graft failure was encountered mainly in patients who underwent prosthetic graft repair. It is in this group that 2 of the 3 early postoperative deaths occurred, from graft thrombosis and mesenteric infarction. Overall, surgical repair was attended with good outcome (77%).