Despite advances in vascular surgical techniques and antimicrobial therapy, aortic graft infection remains a difficult clinical problem to manage. We report a case of secondary paraprosthetic fistula. All complementary investigations were negative and the fistula was diagnosed by laparotomy. In situ replacement of the infected graft was decided despite signs of infection. The postoperative course was complicated by septic shock, successfully treated by organism-specific antibiotic therapy. In conclusion, complementary investigations should not delay laparotomy in patients with a aortic prosthesis presenting with unexplained infection. They must be considered to be suffering from a graft infection until proven otherwise. Conditions in situ replacement of the graft appears to be possible under these.