Direct revascularization of a bronchial artery has been proposed as a measure to alleviate the problem of bronchial ischemia after lung transplantation. To assess the effect of restoration of arterial blood flow to the transplanted bronchus, bronchial mucosal blood flow was measured in a model of modified unilateral lung transplantation in pigs. Laser Doppler velocimetry (LDV) and radioisotope studies using radio-labeled erythrocytes (RI) were used to measure blood flow at the donor main carina (DC) and upper lobe carina (DUC) after 3 h of reperfusion. The recipient carina was used as a reference point; values obtained by LDV and RI were expressed as percentage of blood flow at the recipient carina. Two groups of animals were studied. In group 1 (n = 6) standard unilateral transplantation was performed; in group 2 (n = 6) a left bronchial artery was reimplanted into the descending thoracic aorta of the recipient. No differences were observed between the two groups with respect to preoperative or postoperative gas exchange or hemodynamics. In group 1, bronchial blood flow at the DC was 37.6 ± 2.2% (LDV) and 44.1 ±14.8% (RI) of reference blood flow. At the DUC, blood flow was 54.9 ± 7.7% (LDV) and 61.6 ±25.7% (RI) of normal flow. In group 2, blood flow was increased at the DC as measured by LDV (55.3 ±17.1%; p<0.05) and by RI (60.8 ±25.3%; p< 0.2). A similar increase was found at the DUC (LDV: 81.8 ±19.3%; p < 0.05; RI: 88.6 ±31.0%; p< 0.2). It is concluded that there is a significant gradient of blood flow from intra- to extrapulmonary airways after lung transplantation. Reimplantation of a bronchial artery results in significant improvement of graft bronchial blood flow. Restoration of bronchial perfusion to normal levels, however, cannot be achieved, suggesting a possible defect in the microcirculation of the donor airways. [Eur J Cardio-thorac Surg (1991) 5:561-565].