Postoperative gastrointestinal fistulae occur more often in patients undergoing surgical treatment for oncological reasons than non-oncological reasons. Fistula is associated with a number of serious sequelae and complications: fluid and electrolyte abnormalities, acid-base abnormalities, local and systemic infection and progressive cachexia that increase morbidity, treatment duration and mortality. Development of fistula additionally delays or prevents specific treatment in oncology. For a patient, a fistula is associated with both physical and mental suffering resulting from concern over further therapy.Although the introduction of advanced surgical techniques, intensive postoperative care, total parenteral nutrition and modern enteral nutrition, resulted in decreased postoperative mortality, however the number of patients with gastrointestinal fistulae hospitalized in the departments of surgery is not decreasing. This may result from the fact that many patients still present for treatment in the advanced phase of their malignancy (clinical stage III/IV according to International Union Against Cancer - UICC) and consequently in worse general status, which poses a high risk of postoperative complications and requires more extensive procedures in progressively older patients. Thus gastrointestinal fistulae still remain a serious clinical problem. Main components of treatment of fistulae include: adequate draining, fighting of infections, artificial nutrition and drugs that decrease gastrointestinal secretion (e.g. somatostatin) that are intended to create conditions for spontaneous fistula healing. Some cases may require an early or late surgical intervention.