Growth factors are polypeptides that induce cell mitogenicity, and thus play an important role in the etiology and progression of tumors (1 ). Fibroblast growth factors (FGF) constitute a family of structurally related polypeptides of 146 amino acids, which exhibit a wide spectrum of biologic activities, including angiogenesis or the formation of a vascular network. FGFs are mitogenic towards many mesodermal and ectodermal cell types, and can also induce and/or inhibit differentiation of cells (2 ). These heparin-binding factors are categorized as FGF-1 through FGF-10. Acidic FGF, or FGF-1, is found mostly in brain and other neural tissues. Basic FGF, or FGF- 2, a protein of 18 kDa mw, is one of the most ubiqitous growth factors. It is found in numerous benign and cancerous human and animal tissues, including kidney, prostate, and bladder (3 –6 ). In some cases it has also been demonstrated to have potential as a tumor marker (7 –11 ). One group reported greater recovery of both FGF-2 protein and FGF-2 mRNA from renal-cancer tissue compared to equal amounts of normal renal tissue (5 ). Furthermore, when purified FGF-2 from renal cell carcinoma (RCC) is added exogenously to other established renal tumorcell lines and endothelial cell lines, it demonstrates significant mitogenic activity (6 ). Thus, renal tumors may use FGF-2 in an autocrine manner to sustain themselves.