OBJECTIVES: Open Surgery (OS) of abdominal aortic aneurysms (AAAs) is a major surgical procedure with elevated morbidity and a low but definite mortality. Endovascular repair (EVAR) has now emerged as a minimally alternative to OS, and its effectiveness has now been reported in the literature with reduced peri-operative mortality and complication rates. The aim of this study was to compare the full cost of the two treatments. METHODS: A prospective, observational study was conducted in a Vascular-Surgery Division from October 2003 to April 2004. Data for patients undergoing treatment of an AAA were collected. Cost assessment was carried out from the hospital perspective according to the Activity Based Costing principles. RESULTS: Data for 44 patients were gathered: 73% underwent OS and 27% EVAR. The mean age was 66.7 (±16.7) years and 7% of the patients were female. Comorbidity rates were similar in the two treatments group. There was no difference in mean hospital length of stay (LOS) between the two options (ten days). Mean post-operative LOS was 6.5 days (±4), with significant difference between the two groups (OS 7.5±4 vs. EVAR 3.5±0.6, p<0.0001). Intensive therapy was necessary only for OS patients (28%). The study revealed that the overall mean cost to treat an AAA, irrespective of the technique used, was €11,578.34 (€ 11,063.31 OS vs 12,971.56 EVAR). A sub-analysis was performed for complicated patients alone and the mean cost was € 13,487.46, with a difference between the two treatments tending almost to zero. The use of post-operative resources differed between the two treatments, resulting in differences for the mean post-operative costs (€ 5,686.07 for OR vs € 2,185.49 for EVAR). CONCLUSIONS: Stent graft treatment of AAAs has been shown to be effective in reducing the amount of nursing assistance, LOS and the need for intensive therapy at the post-operative stage.