We report the first example of smooth-muscle proliferations occurring in an allograft lung implanted in a recipient who had end-stage emphysema. Smooth-muscle proliferations were detected 46 months following transplantation in a 53-year-old woman. The lesions involved the airways and were bronchoscopically undetectable. Posttransplant smooth-muscle tumors have been described in liver transplant patients and are thought to be due to Epstein-Barr virus. Evidence of virus infection was not found in the current case.