Fifty-three patients with enterocutaneous fistulas were treated nonoperatively. While most of the fistulas resulted as a complication of surgery, other causes included inflammatory disease, trauma, and malignancy. Fistulas originated from the esophagus (n = 4), stomach (n = 4), duodenum (n = 5), small bowel (n = 27), colonic-small bowel anastomosis (n = 2), colon (n = 10), and Hartmann pouch (n = 1), and included both high-output (n = 29) and low-output (n = 24) types. Nonoperative management resulted in spontaneous fistula closure in 57%. Most of the spontaneous closures (83%) occurred within 2 months of treatment. Spontaneous closure rates were similar for low-output and for high-output fistulas (52% vs 63%), but the treatment duration was longer for high-output than for low-output fistulas (mean treatment duration, 17 days vs 41 days). Colonic fistulas were particularly difficult to manage and closed spontaneously in only 10% of patients (one of 10).