The authors assess clinical and radiographic findings of pulmonary nodules and masses after lung and heart-lung transplantation. One hundred and fifty nine patients who survived at least 3 months after lung and heart-lung transplantation were followed by serial chest radiographs for a median of 27 months. Single or multiple lung nodules or masses were noted at chest radiography in 15 (9.4%) of 159 patients. Imaging findings and causes of these nodules and masses were reviewed retrospectively. Infection was found in 10 (6%) of 159 patients. Specific pathogens (11 pathogens in 10 patients) were Aspergillus (n = 4), Mycobacteria (n = 4), and other bacteria (n = 3). Noninfectious causes were found in 5 (3%) of patients and included B-cell lymphoma (n = 2), bronchogenic carcinoma (n = 2), and pulmonary infarcts (n = 1). Nodules and masses appeared a median of 11 months after transplantation (range: 0.2 to 36 months). Five patients (33%) had single lesions; the other 10 (67%) patients had multiple lesions (range 2 to 50). Aspergillus lesions were most commonly located in the upper lobes, were cavitary in three of four patients, and all were fatal. Nodules and masses arose in the transplanted lung in 12 (80%) of the patients, and in the native lung in 3 (20%) of the patients (2 bronchogenic carcinoma, 1 M. tuberculosis simulating bronchogenic carcinoma). Nodules and masses detected by chest radiography are not uncommon (9.4%) after lung and heart-lung transplantation. Infections are more common than noninfectious causes of posttransplant nodules and masses. Specific clinical and imaging characteristics may provide clues to etiology.