The use of heparin in Crohn's disease and associated fistulous disease was initiated as an open-labeled trial. Recent open-labeled series suggested a benefit of heparin in Crohn's disease. Heparin has not been reported to be tried for treatment of fistulous disease which can be a particularly difficult treatment delimma. The rational is similar to the placebo- controlled trial of heparin in ulcerative colitis. A hypecoaguable state has been detailed in association with flares of Crohn's disease and ulcerative colitis. This hypercoaguable state may reflect micorthrombi being deposited in the intestinal vasculature leading to the clinical and pathological characteristics of Inflammatory Bowel Disease. Heparin maybe an agent which would reverse this hypercoaguable state and interfere with the progression of disease. While the beneficial mechanism of action of heparin is likely to be at least in part mediated by its anticoagulant properties, other possible functions of heparin may contribute to controling flares of Crohn's disease and healing fistulea. We have recently initiated this study enrolling to date two patients with fistulae and two patients with Crohn's disease with refractory diarrhea. Both patients with fistulous disease have shown dramatic improvement; one patient with refractory diarrhea failed to show any improvement and in the remaining patient, there has been inadequate time to evaluate his progress.