Pulmonary lobar transplantation provides a clue to the acute donor shortage. To examine the experimental and clinical applicability of lobar transplantation, the authors observed the extent of lung expansion and infiltrate in the allografted lobe through the sequential analysis of the early chest roentgenograms. MATERIALS AND METHODS: Twenty two mongrel dogs weighting 17 kg on average were used. Donor lung bloc was taken and flushed with Euro-Collins solution. The left lower lobar bloc was procured and implanted in the pneumonectomized recipient dog. The anastomosis was performed in the order of the pulmonary vein, artery, and bronchus. To assess the radiological pattern in the lobar allograft, a grading system was designed according to the extent of lung expansion and infiltrate. RESULTS: A) Expansion pattern: Good to excellent lung expansion was seen on postoperative day 0 in 6 out of 10 dogs; on day 1, 4/7; day 2, 3/12; day 3, 1/1; and day 4, 1/3, respectively. Radiographs on day 6, 7, and 12 also showed good expansion in one dog. B) Lung opacity pattern: Clear to minimal infiltrates were seen on day 0 in 8 out of 10 dogs; day 1, 7/17; day 2, 2/12; and day 4, 1/3. The same appearances were detected in a single dog on day 6, 7, and 12. C) Expansion-opacity correlation pattern: Radiographs on postoperative day 0 showed good expansion with mild infiltrates, and excellent expansion with minimal infiltrates were observed on day 1 in 3 out of 17 dogs, day 2, 1/12; and day 4, 1/3, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)