Transabdominal aortic replacement is the most widely accepted approach for aortic surgery. Several controlled studies report a more favorable outcome after an extraperitoneal incision, yet there are an equal number of papers with contradictory results. The aim of our study was to assess operative trauma after aortic surgery, depending on whether transperitoneal or extraperitoneal access was used. As a parameter for the extent of the surgical trauma the concentration of Interleukin 6 and acute phase proteins (CRP) was measured pre-, 6 h and 24 h after aortic surgery. One group consisted of 34 patients scheduled for aortic surgery for exclusion of an abdominal aortic aneurysm. The second group consisted of 26 patients who were operated on for aorto-iliac occlusive disease. Each group was subdivided into an equal group of patients operated on either extra- or transperitoneally. In the retroperitoneal aneurysm patients, a posterolateral access was favored, and in patients with occlusive disease an extraperitoneal anterolateral approach was chosen. As a result patients with an extraperitoneal incision and aorto-iliac occlusive disease required less postoperative respiratory support than those operated on transperitoneally. In this subgroup of patients there was a significantly reduced synthesis of Interleukin 6 and CRP. When a retroperitoneal posterolateral approach was required in aneurysm patients, there was no difference between groups. We conclude from our data that only patients with limited infrarenal aortic access can benefit, from the retroperitoneal incision in terms of a reduced immunological reaction.