We examined the effects of human recombinant basic fibroblast growth factor (bFGF) on the proliferation and migration of cultured dog smooth muscle cells (SMCs) and endothelial cells (ECs) and the effect of continuous local boundary layer infusion of bFGF on intimal hyperplasia in endarterectomized dog artery. In vitro proliferation and migration of dog SMCs or ECs were performed using direct counting and Boyden's chamber, respectively. At a dose of 10 ng/mL, bFGF significantly promoted both SMC and EC proliferation (7- and 4-fold, respectively) and migration (2.3- and 1.9-fold, respectively). Six dogs underwent bilateral carotid endarterectomies. A newly designed local infusion device with an osmotic pump continuously delivered bFGF to one artery or vehicle solution to the contralateral artery for 14 days. The intimal thickness and area in the bFGF-treated vessels were increased by 72 and 81%, respectively, compared with control arteries (P < 0.05). As assessed by the bromodeoxyuridine index, the proliferative activity was increased by 73% in bFGF-treated arteries (P = 0.03). Furthermore, cell proliferation at the distal anastomoses of local infusion device was significantly increased in the bFGF-infused grafts compared with distal anastomoses in the control grafts (13.24 +/- 1.24% versus 5.24 +/- 1.01%, P < 0.01). These data demonstrate that human recombinant bFGF has a potent effect on dog SMC and EC proliferation and migration, and that local infusion of exogenous bFGF significantly enhances the intimal hyperplasia formation and cell proliferation to vascular injury. We conclude that the bFGF pathway may contribute to the development of intimal hyperplastic lesions.