A new surgical procedure was devised for the experimental homograft of the lung. The pulmonary artery and vein and bronchus were anastomosed under the operation microscope using interrupted sutures in group W (30 outbred Wistar rats) and continuous sutures in group F (7 inbred F344/Ducrj Rats). Mean ischemia time during the operation was 95.3 +/- 10.3 min in the group W and 55.6 +/- 5.8 in group F. Eight out of 30 rats (27%) of group W and all rats of group F survived more than 24 hr after the surgery. Pulmonary functions of grafted lungs were evaluated by serial x-rays and the perfusion ratio was 27.4 +/- 11.6% (mean +/- S.D.) in group W and 25.4 +/- 7.7% in group F. A patent opening of the hilar anastomosis in these rats was confirmed at autopsy. This model with continuous suture would be useful for the rat lung transplantation.