We have previously demonstrated increased fibroblast growth factor-2 (FGF-2) expression in a lamb model of increased pulmonary blood flow secondary to congenital heart disease, which may contribute to the associated increases in pulmonary arterial muscularization. However, the mechanisms underlying these increases in FGF-2 expression remain to be identified. Initially, we found that exogenous FGF-2 increased endogenous FGF-2 promoter activity and protein levels in ovine pulmonary arterial smooth muscle cells (PASMC). Further, we found that these increases in FGF-2 expression were mediated by increases in superoxide levels via NADPH oxidase activation. In addition, FGF-2-mediated increases in FGF-2 expression and PASMC proliferation were attenuated by inhibition of PI3 kinase, Akt and NADPH oxidase. Increases in FGF-2 expression could be stimulated by other factors known to increase ROS signaling in PASMC (ET-1 and TGF-1) while antioxidants attenuated these increases. Deletion constructs localized the growth factor- and ROS-sensitive region within the proximal 103bp of the FGF-2 promoter and sequence analysis identified a putative hypoxia response element (HRE), a DNA binding site for the ROS-sensitive transcription factor HIF-1. Stabilization of HIF-1 increased FGF-2 promoter activity, while mutation of the putative HRE attenuated FGF-2-induced FGF-2 promoter activity. Further, FGF-2 increased HIF-1 protein levels and consensus HRE promoter activity in PASMC via antioxidant-sensitive mechanisms. Thus, we conclude that FGF-2 can stimulate its own expression in PASMC via NADPH oxidase-mediated activation of ROS-sensitive transcription factors including HIF-1. This positive feedback mechanism may contribute to pulmonary vascular remodeling associated with increased pulmonary blood flow.