Femoral noninfected anastomotic aneurysms. A report of 56 cases. Fifty-six femoral non infected anastomotic false aneurysms (FAAs) were observed in 49 patients admitted to the Institute of Vascular Surgery, University of Milan, from 1975 to 1988; in 6 patients they were bilateral. These aneurysms developed after primary revascularization procedures at a mean interval of 66 months (range 12 to 156 months); one recurred after reparative surgery. Forty-four FAAs (78.6%) were asymptomatic, whereas 3 (5.3%) were complicated by acute expansion and 9 (16.1%) by thrombosis. Host vessel degeneration was the cause of aneurysm formation in most cases. A history of hypertension was present in 30% of the patients. All anastomotic aneurysms were operated upon except for one small aneurysm that was asymptomatic. In 5 patients aneurysm resection was carried out on both sides. The surgical technique was endoaneurysmectomy in all the cases with insertion of an interposition graft in 48 cases, a fabric patch in 2 cases and prosthesis re-anastomosis in 5 cases. One case of peripheral embolization occurring in the early postoperative period was successfully treated and there was no operative mortality. In our opinion elective repair of these aneurysms should be recommended whenever possible because of their propensity to develop serious complications and the operative morbidity is low. 