Homogenization of human benign prostatic hyperplastic tissue in high ionic strength alkaline buffer containing protease inhibitors resulted in the isolation of a 17,400 molecular weight growth factor. When tissue was homogenized in ammonium sulfate at pH 4.5 without protease inhibitors a smaller, 16,600 dalton, growth factor was isolated. Both growth factors reacted with antisera against synthetic peptides whose sequences corresponded to the amino-terminal (1-12), Internal (33-43) and carboxyl-terminal (135-145) portions of basic fibroblast growth factor (bFGF). This suggested that the smaller growth factor was not a truncated form of (1-146) bFGF and that the larger growth factor may contain additional sequences. Amino-terminal sequencing showed the larger growth factor to have the sequence: Ala-Ala-Gly-Ser-Ile-Thr-Thr-Leu-Pro-Ala-Leu-Pro-Glu-Asp-Gly-Gly-Ser-Gly- Ala-Phe-Pro-. These results show that the larger growth factor is an 8 amino acid extended from of (1-146) bFGF and it is likely that the smaller growth factor is a proteolytic cleavage product of the larger growth factor produced during the extraction procedure.