Basic fibroblast growth factor (bFGF) is a mitogenic factor that is implicated in smooth muscle cell growth in atherosclerosis and vascular restenosis. In this study, we examined the effect of bFGF on the expression of the interstitial collagenase gene in human vascular smooth muscle cells. Results from Northern transfer analysis showed that bFGF increased collagenase mRNA levels greater than threefold as early as 24 h. Collagenase pre‐mRNA levels were elevated approximately threefold by bFGF, according to RT‐PCR analysis. Transient transfections of the smooth muscle cells with a 4.4‐kb human collagenase promoter‐CAT reporter gene, however, failed to show upregulation of the promoter activity by bFGF. Interestingly, transfections with deleted fragments containing promoter sequences from ‐1047 to ‐2271 resulted in modest stimulation of the collagenase‐CAT promoter activity by bFGF. bFGF did not alter the stability of the collagenase mRNA, as demonstrated by degradation studies. The enhanced collagenase mRNA levels elicited by bFGF were reflected in increased amounts of collagenase protein that were detected by Western blot analysis. In summary, bFGF upregulates the interstitial collagenase expression, resulting in turnover of the extracellular matrix, an event that could facilitate smooth muscle cell migration and proliferation during the early stages of atherosclerosis and restenosis. J. Cell. Biochem. 65:32–41. © 1997 Wiley‐Liss, Inc.