Over the decades the advent of advanced surgical techniques, antibiotics, management of acid-base and electrolyte disorders, monitoring and support of cardiorespiratory function, have greatly implemented the treatment of patients with gastro-intestinal fistulas, resulting in most series in a mortality of approximately 20%. The apparent clinical benefit of sophisticated parenteral nutrition has not further reduced mortality because in the seventies patients in most series were older, sicker, had more advanced cancer, underwent bigger operations and were more at risk in almost every respect. In recent series mortality is almost exclusively determined by uncontrolled sepsis. It is therefore imperative to control intra-abdominal infection because ongoing sepsis ultimately nullifies the effect of other therapeutic modalities. When infection is controlled however nutritional support may serve several purposes. It may relieve malnourishment. It may decrease gastro-intestinal, biliary and pancreatic secretion allowing fistula output to diminish and sometimes fistulae to heal spontaneously. It may allow a potential future operative field to quiet down. With adequate nutritional support fistulae may heal spontaneously (lateral, no distal obstructions, no adjacent abscesses, good quality bowel). Others may be surgically treated with the patient in good nutritional state and with a favourable local situation. Crohn's fistulae heal spontaneously in a large percentage (80%) but have to be operated after closure because the cause of the fistulae is almost invariably an irreversibly stenosed fibrotic bowel segment so that fistulae may recur after resumption of oral feeding. In unfavourable fistulae (total disruption, adjacent abscesses, bad quality bowel) infection is often difficult to control.(ABSTRACT TRUNCATED AT 250 WORDS)