A 16 year old man underwent an allogeneic bone marrow transplantation (BMT) from an HLA identical sibling donor for acute lymphoblastic leukaemia in 1984. He developed chronic graft versus host disease involving the skin and kidneys. At day 400 after BMT his condition was complicated by obstructive airways disease, which was partially responsive to azathioprine and steroids. Five years after withdrawal of immunosuppressive treatment he developed dyspnoea and decreased pulmonary function test results, and steroid treatment was resumed. Fibrobronchoscopy revealed the presence of a mucoepidermoid carcinoma in the left main bronchus. After surgical laser resection, there was gradual clinical and functional improvement. There was no evidence of recurrence one year after surgery.