Although cutaneous graft-vs.-host disease (GVHD) has been noted after autologous hematopoietic cell transplantation, intestinal involvement has not been well documented. We evaluated 197 patients undergoing autologous transplantation for intestinal symptoms; the source for hematopoietic cells was marrow (n=32), peripheral blood stem cells (n=146), or both (n=19). Patients with persistent nausea, vomiting, and anorexia after day 20 underwent upper intestinal endoscopy and mucosal biopsy. Eight patients (4.1%) had diffuse edema, erythema of gastric mucosa, and histological evidence of lymphocytic gastritis with focal apoptosis of crypt epithelial cells-typical of the findings in acute GVHD. All studies for viral, fungal, or bacterial causes were negative. Two patients showed evidence of GVHD in skin and liver, respectively. All patients received 1 mg/kg/day of oral prednisone for 10 days; symptomatic improvement often occurred within days of therapy onset. At the end of corticosteroid treatment, complete resolution of symptoms was seen in all eight patients. In one patient, elevated serum alkaline phosphatase levels gradually normalized over the ensuing 3-4 weeks. When followed up 3 months after treatment, all patients remained symptom-free without evidence of recurrent intestinal symptoms. We concluded that recipients of autologous hematopoietic cells may develop intestinal symptoms caused by a lymphocytic gastritis that is typical of acute GVHD. Patients with this syndrome promptly responded to treatment of a short course of prednisone. The pathogenesis of gastric epithelial damage after autologous transplant is unknown.