Following heart-lung transplantation two of 21 patients who survived more than 100 days developed post-transplant lymphoproliferative disease. Both presented with localised ulcerative bronchitis documented at flexible bronchoscopy four months after transplantation. Histological examination showed necrosis with acute inflammation and ulceration. Case 2 demonstrated lymphoproliferative disease from biopsies subsequently taken at rigid bronchoscopy. Case 1 later developed lung nodules and a monoclonal high grade B cell non-Hodgkin's lymphoma was confirmed by an open lung biopsy. The bronchoscopic features described should alert clinicians to post-transplant lymphoproliferative disease as an underlying diagnosis and suggest that bronchus associated lymphoid tissue is the initial site for clonal proliferation in the disease.