Aim. To analyze the results of treatment of patients with rare forms of complicated abdominal aortic aneurysm namely aorto-enteric and aorto-caval fistulae. Material and methods. 3 cases of aorto-enteric fistula (with jejunum and sigmoid in two and one cases respectively) and 5 cases of aorto-caval fistula were revealed among 149 patients operated for complicated abdominal aortic aneurysms for the period from 2005 to 2014. All patients underwent abdominal aortic replacement using synthetic vascular graft. In patients with aorto-caval fistula anastomosis between the vena cava and aortic lumen was sutured through the aneurysmal sac lumen. Bowel resection (1), the seam of the bowel wall with Brown’s interintestinal fistula (1) and the Hartmann’s procedure (1) were performed for aorto-enteric fistula. Results. In postoperative period 3 patients died due to hemorrhagic shock with DIC (2) and sepsis with multiple organ failure, which accounted for 33.3 and 40% for each disease respectively. Survivors were followed for 22—51 months after surgery. The reasons of adverse outcomes including late and inadequate diagnosis as the most important were analyzed.