Intimal smooth muscle cell accumulation is regarded as an important component of atherosclerotic plaque formation, angioplasty-induced restenosis, and vascular graft occlusion. Vascular smooth muscle cells can both express and respond to acidic fibroblast growth factor (aFGF) and basic fibroblast growth factor (bFGF); therefore, under certain conditions these polypeptides may regulate smooth muscle cell growth in an autocrine manner. Previous studies using smooth muscle cells cultured in vitro have identified factors that can enhance aFGF and bFGF gene expression. In this study, we assayed fibroblast growth factor gene expression in a spontaneously immortalized rabbit smooth muscle cell line. In contrast to "normal" rabbit smooth muscle cells, these immortalized cells acquire an altered morphology and enhanced proliferative rate during; cell passaging in vitro. Both "normal" and immortalized rabbit smooth muscle cells express bFGF but not aFGF transcripts. RNA gel blot hybridization, reverse transcription/polymerase chain reaction amplification, and Western blotting techniques demonstrate that bFGF expression in the immortalized smooth muscle cell line increases as a function of passage level. This continuous cell line should prove valuable for studying both the regulation of bFGF synthesis and the control of vascular smooth muscle cell proliferation.