Unexpected anatomical and clinical features of abdominal aortic aneurysm (AAA) may be encountered by the vascular surgeon creating technical problems that increase the normally low mortality rates of this affection. One such variant is the so called inflammatory aneurysm (IA) as a characteristic fibrosis involving the arterial wall and thus surrounding structure scan be observed. In our series of 525 patients affected by AAA the incidence of IA was about 4% (19 cases). Two groups of patients were considered: group A, including all the atherosclerotic patients, and group B 19 patients affected by IA. The latter group referred to a typical painful symptomatology in 84% of the cases: this element is of interest as only 20% of the cases of group A complained of pain. No other significant clinical or laboratory data were recorded which could allow the surgeon to perform a pre-operative differential diagnosis. In all 19 cases that underwent surgical treatment there was a 2-3 cm thick aneurysmal wall with a shiny white surface adhering to the IV portion of the duodenum, vena cava and iliac vessels and in some cases to the ureters. Histological examination of specimens of the aortic wall showed evident signs of atherosclerosis of the media and marked fibrotic thickening of the adventitia with the presence of lymphocyte aggregates: a sign of chronic inflammation. As what concerns indications and surgical treatment, there are no substantial differences. Pre-operative differential diagnosis can be made with CAT scan and ultrasound and the usual operative manoeuvres of aneurysmorrhaphy should be modified.