Acute intestinal graft-versus-host disease (GVHD) develops in about 30-50% of allogeneic bone-marrow transplant recipients: 10-20% have gastrointestinal emergencies (hemorrhage or perforation). Mortality reaches 30-60% in patients with acute, grade 2-4 GVHD. We studied 36 bone marrow recipients in whom acute intestinal GVHD developed. Seven had gastrointestinal emergencies: 4 severe gastrointestinal bleeding and 3 acute peritonitis. Three patients with gastrointestinal bleeding and one patient with peritonitis responded to medical therapy. Three needed surgery: one with bleeding and two with peritonitis, while 1 patient had embolization. Of the 7, two patients died, one after embolization and one after surgery. Two of the three surgically-treated cases are still alive several years after operation. From this experience we feel that surgery for gastrointestinal bleeding in acute GVHD is indicated only when medical treatment fails. Severe neutropenia, thrombocytopenia (<10.000 x mm3) and blood cultures positive for CMV have an unfavorable prognostic value.