An abnormal pulmonary vasculature may be an important component of bronchopulmonary dysplasia (BPD). We examined human infant lung for the endothelial cell marker PECAM-1 and for angiogenic factors and their receptors. Lung specimens were collected prospectively at approximately 6 h after death. The right middle lobe was inflation fixed and part of the right lower lobe was flash frozen. We compared lungs from infants dying with BPD (n = 5) with lungs from infants dying from nonpulmonary causes (n = 5). The BPD group was significantly more premature and had more days of ventilator and supplemental oxygen support, but died at a postconceptional age similar to control infants. PECAM-1 protein and mRNA were decreased in the BPD group. PECAM-1 immunohistochemistry showed the BPD group had decreased staining intensity and abnormal distribution of alveolar capillaries. The dysmorphic capillaries were frequently in the interior of thickened alveolar septa. The BPD group had decreased vascular endothelial growth factor (VEGF) mRNA and decreased VEGF immunostaining, compared with infants without BPD. Messages for the angiogenic receptors Flt-1 and TIE-2 were decreased in the BPD group. We conclude that infants dying with BPD have abnormal alveolar microvessels and that disordered expression of angiogenic growth factors and their receptors may contribute to these abnormalities.