Human fibrin sealant (Tissucol) has been used in surgery for its haemostatic and sealing actions and stimulating effect on tissue regeneration. Recently it has been used in endoscopy, but controlled trials are not yet available. The aim of this study was to evaluate the efficacy of Tissucol on the healing rate of duodenal ulcers (DU). Thirty nine previously untreated DU patients received ranitidine 150 bid plus endoscopically applied either placebo (19 patients) or Tissucol (20 patients). Sixty-five percent of the patients in the Tissucol group and 21% in the control group healed after two weeks (p less than 0.02), 75 and 52.6% respectively after 4 weeks (NS). The endoscopic application of Tissucol seems to influence the healing of duodenal ulcer and its use could be suggested in selected patients with DU.