Malnutrition is common in patients with gastrointestinal tract fistula, and is an important cause of the high mortality seen with this surgical complication. A prospective review of three years' experience in the management of fistulae with parenteral nutrition was undertaken, and the results obtained were compared with those in a group of patients treated prior to the introduction of this form of therapy. The use of parenteral nutrition resulted in a reduction of the mortality from 63% to 23% in unselected cases. The mortality was zero where parenteral nutrition was used in patients under 65 years of age with non-malignant disease. With parenteral nutrition therapy, the fistulae in almost all cases closed spontaneously, in contrast with a high proportion requiring operation (20 in 38 cases) where parenteral nutrition was not used. It is concluded that all patients with significant gastrointestinal fistula should be given appropriate parenteral nutrition as their prime mode of therapy.