AWARENESS of the more common diagnostic variabilities of ruptured and expanding abdominal aortic aneurysms has, happily, become quite universal in recent years. One particular clinical picture caused by the rupture of an intra-abdominal (usually aortic) aneurysm is, however, much less well understood—the picture of the sealed rupture of a small aneurysm that very closely mimics the complex of signs and symptoms of intra-abdominal and, in particular, retroperitoneal sepsis.1 In recent years we have observed seven such cases; in all, the correct diagnosis was not made or was tragically delayed. A review of these cases yielded findings the report of which may help lessen the diagnostic difficulties which these enigmatic and desperately serious problems present to the surgeon. Material The cases to be described belong in the clinical category of ruptured aneurysms but certain characteristics set them apart. In all, there were objective signs of an inflammatory or septic