Tumor-promoting phorbol esters have been shown previously to either induce or repress the expression of numerous cellular genes, and this property is likely to be important for the in vitro and in vivo biological effects of these compounds. In this report, we demonstrate that phorbol 12-myristate 13-acetate induces the accumulation of basic fibroblast growth factor mRNA and protein in human dermal fibroblasts. In contrast, acidic fibroblast growth factor expression was unaffected by this compound. The enhancement of basic fibroblast growth factor gene expression by phorbol 12-myristate 13-acetate was blocked by the isoquinolinesulfonamide derivative H7, a potent inhibitor of protein kinase C. Two additional tumor promoters that bind to and activate protein kinase C, phorbol 12,13-didecanoate and mezerein, also increased basic fibroblast growth factor mRNA levels. Basic fibroblast growth factor is a mitogen for many cell types and can stimulate angiogenesis; thus, some tumor promoter-induced cellular responses may be mediated by this polypeptide.