Recognized manifestations of acute graft-versus-host disease (GVHD) of the gastrointestinal (GI) tract include secretory diarrhea, abdominal pain, and, at times, hemorrhage. In a review of 469 patients undergoing allogeneic bone marrow transplantation (BMT) from matched sibling donors at our institution, we have recognized a syndrome of upper GI GVHD. This syndrome, presenting clinically as anorexia, dyspepsia, food intolerance, nausea, and vomiting, was recognized and confirmed histologically in 62 patients (13% by Kaplan-Meier projection) at the initiation of systemic GVHD therapy, a subset of the 197 patients developing grade II through IV GVHD. These 62 patients with upper GI GVHD were significantly older than the overall BMT population and older than the cohort with grade II through IV GVHD, as well. Of the 62 patients, 25 had upper GI GVHD accompanied only by limited (stage 1 and 2) skin GVHD; 13 others with upper GI GVHD plus limited skin involvement at initial presentation later progressed to more extensive multiorgan involvement; 24 others presented with upper GI along with other organ GVHD. This upper GI GVHD syndrome, first recognized at our center in 1983, has been diagnosed with increasing frequency (22% +/- 5%) in the most recent 5-year interval. The upper GI GVHD syndrome is more responsive to immunosuppressive therapy than grade II GVHD defined by Seattle criteria, with complete and continuing responses to treatment observed in 71% +/- 17% (95% confidence interval) of those with the upper GI GVHD syndrome compared with only 37% +/- 10% complete responses in other patients with grade II GVHD (P = .002). Patients failing immunosuppressive therapy for upper GI GVHD often progress to symptomatic lower GI involvement, suggesting that this syndrome may be an earlier and perhaps more treatable manifestation of this unique intestinal immunopathology, which is followed by chronic GVHD in 74% of patients. While upper GI GVHD symptoms are nonspecific and require invasive histologic and microbiologic studies to confirm the diagnosis, we believe this syndrome has been underreported after allogeneic BMT and propose its recognition within the clinical GVHD scoring system.