Graft-vs-host disease, characteristically a major complication of allogenic hematopoietic stem cell transplantation, is rare after solid organ transplantation. We report a 50-year-old man who presented with abdominal pain, vomiting, and diarrhea shortly after bilateral lung transplantation. Colonoscopy with biopsy revealed diffuse severe active colitis with ulceration and crypt apoptosis consistent with graft-vs-host disease colitis. The diagnosis was confirmed by the presence of donor lymphocytes in the peripheral blood. His symptoms were refractory to corticosteroids but responded to the addition of infliximab and extracorporeal photophoresis. He remained in remission 17 months later.