Aim: Ruptured aortic aneurysm can be tt atusc of acute abdomen. Nowadays using modern diagnostic techniques diagnosis is very easy. W'e report a particular can' of a misdiagnosed ruptured aortic aneurysm. (!ase Report: Man 65 y.o. admitted to hospital for abdominal pain and stipsis. After I week he developed acute abdomen with muscotar rigidity and mild acute anemia, hew days before contrast studies showed a sigmoid diverticular disease. At laparotomy a ruptured aortic aneurysm seated from retroperitoneal fascia and extended to abdomi na! walls up to rectus abdominis muscles tons found. Conclusions: In case of acute abdomen with muscolar rigidity and acute anemia the diagnosis of rectus abdominis muscles hematoma caused by ruptured aortic aneurysm must be considere