The effect of bronchial circulation on wound healing at the site of anastomosis after right upper sleeve lobectomy was studied in dogs. In two dogs (Group I), the bronchial arteries were carefully preserved during the sleeve lobectomy. In 16 dogs (Group II), only sleeve lobectomy was performed after all bronchial arteries in the hilum were ligated. In three dogs (Group III), the site of anastomosis was wrapped by a Penrose drain after sleeve lobectomy. In three other dogs (Group IV), the site of anastomosis was wrapped with a free pleural flap after sleeve lobectomy. In another group of 11 dogs (Group V), the anastomotic site was wrapped with a pedicled pleural flap. The dogs in Group I were put to death immediately and bronchial arterial circulation was recognized to consist primarily of systemic arterial blood. In Group II dogs, bronchial arteries distal to the anastomosis filled with pulmonary arterial blood immediately after the sleeve lobectomy. Although the majority of bronchial arteries became filled with systemic arterial blood with time, some vessels were filled with pulmonary arterial blood even 7 days after the sleeve lobectomy. In Group III dogs, wound healing at the site of anastomosis was severely delayed, and 7 days after the sleeve lobectomy the majority of bronchial arteries in the bronchial wall distal to the anastomosis were filled with pulmonary arterial blood. In Group IV dogs, the state of wound healing at the bronchial anastomotic site was similar to that of Group III dogs. In Group V, although the state of wound healing at the anastomosis was relatively good in most of the animals, the pedicled pleural wrap did not significantly improve bronchial circulation over that of Group II.