Peptide growth factors are involved in hypoxia-mediated neonatal pulmonary vascular remodeling. The role of hypoxia in the release of selected peptide growth factors from neonatal porcine pulmonary artery smooth muscle cells (PASMC) was examined. PASMC were exposed to different oxygen tensions and the cells were counted electronically and the conditioned media analyzed for basic fibroblast growth factor (bFGF), endothelin-1 (ET-1), platelet-derived growth factor (PDGF), and vascular endothelial growth factor (VEGF). The effect of conditioned media on PASMC proliferation was also measured. Hypoxia (1% oxygen) and hypoxia-conditioned media increased PASMC numbers, and this mitogenic effect was abolished by anti-bFGF, but not by anti-PDGF or anti-VEGF. Hpyoxia increased bFGF and VEGF release but not PDGF or ET-1. This suggests that PASMC-derived bFGF and VEGF may participate in hypoxic neonatal pulmonary vascular remodeling.