A rare case with mycotic abdominal aortic pseudoaneurysm due to Salmonella Infection is described. A 75 year-old female had been diagnosed as an abdominal aortic aneurysm by ultrasonics at the other hospital during the examination of fever of unknown origin and abdominal pain. At admission to our hospital, the temperature was 39.5°C. A pulsatile mass, about the size of five cm in diameter, was present with no inflammatory findings in the abdomen. Ultrasonics and angiography revealed a saccular infrarenal aortic aneurysm. The blood culture was positive for Salmonella choleraesuis. Aneurysmectomy and graft interposition were performed five weeks after admission, because of enlargement of the size of aneurysm and the continuing infective signs in spite of antibacterial therapy. The patient narrowly escaped from rupture of the pseudoaneurysm by the body of third lumber vertebra. On microscopic examination, infective findings were seen in the wall of pseudoaneurysm. After treatment with antibiotics for four weeks, the patient was discharged from the hospital. She remains asymptomatic for a year after the operation. Only eight cases of mycotic abdominal aortic aneurysm have been reported previously in Japan, and five cases, including our case, were due to Salmonella infection. The results of this surgical operations, carefully considered for infection, were good, but it seems better to select alternatively the surgical operation as soon as possible when antibacterial therapy is not effective.