Pulmonary hypertension (PH) has been widely stated as a relative contraindication to bronchoscopic lung biopsy (BLB) because of the potential risk of excessive bleeding. There are few data to support this contention. This risk factor was studied in an animal model of acute PH. Ten adult sheep underwent pulmonary artery (PA) catheterization followed by six BLBs of the right apical lobe and the amount of biopsy-induced bleeding was quantitated. In five of the animals, the mean PA pressure was elevated before bronchoscopy by continuous air embolization through the proximal port of the PA catheter (mean PA pressure, 32.8 ± 4.8 mm Hg). The mean PA pressure for the five control sheep was 12.2 ± 5.0 mm Hg. There was not a significant increase in blood loss for the experimental animals (mean aspirated blood, 2.6 ± 3.1 ml) compared to the controls (mean aspirated blood, 1.0 ± 1.0 ml). Histopathologic correlation supported this finding; gross and microscopic assessments of the apical lobes revealed no evidence of larger zones of hemorrhage for the experimental group. In an ovine model of acute PH, there is no increased risk of bleeding from BLB.