Inflammation and fibrosis do not only appear in an "inflammatory" aneurysm, but also in "ordinary" abdominal aortic aneurysms. In this study inflammatory changes in 130 abdominal aortic aneurysms were studied and related to patients' clinical records. According to histopathological criteria five different degrees of inflammation (Histological Inflammation Scale of Aneurysms) were found and patients were classified according to these criteria: grade A or mixed acute/chronic inflammation (4.5%); grade 0 or no inflammation (16.2%); grade 1 or mild chronic (57.7%); grade 2 or moderate chronic (16.2%); and grade 3 or severe chronic inflammation (5.4%) corresponding to an "inflammatory" aneurysm. Patients with grade 3 or an "inflammatory" aneurysm were younger (p = 0.013), were all symptomatic (p = 0.02), showed no associated iliac or femoral aneurysms (p = 0.03), were only recognised peroperatively and had elevated erythrocyte sedimentation rates (p = 0.0002). No other differences could be demonstrated between sex, risk factors, cardiovascular diseases, previous abdominal operations, bacterial culture, aneurysm diameter, white blood count, cholesterol level in-hospital mortality when compared to the degree of inflammation.