There is a wide variation in reported operative mortality rates for ruptured abdominal aortic aneurysm, ranging from 14 to 70 per cent. Although many factors influence this variation, such as the expertise and facilities available at an individual institution, considerable differences could be due to variations in the pattern of referral and the proportion of cases accepted for operation. In this paper a classification applicable to all patients with ruptured aortic aneurysm is proposed; it has been applied prospectively to 100 consecutive patients with ruptured abdominal aortic aneurysm referred to the Edinburgh Vascular Surgical Unit. The classification illustrates how surgical mortality rates ranging from 29 to 52 per cent may be reported using the same mortality data. Two major benefits may derive from the use of such a standard reporting system. Firstly, it allows management deficiencies to be identified easily and, secondly, it should facilitate comparison of results reported from different centres.