SummaryFive patients with endoscopically demonstrable lesions of Crohn’s disease of the colon were treated with human fibroblast interferon for periods of 3 to 6 weeks. In two cases objective improvement was observed, i.e. disappearance of a chronic perianal inflammation mass and of acute mucosal lesions in the rectum. In two other cases there was marked clinical improvement but without change in endoscopic appearance of the colon. The fifth patient, who presented with a sigmoidovesical fistula, did not respond to the therapy.