Two growth factors have been purified homogeneously from bovine brain by multistep procedure. [Roy R. Lobb et al. (1984), Denis Gospodarowicz et al. (1977)] Two distinct fibroblast growth factors were purified by haparin-affinity with 1.0M and 2.0M sodium chloride, and its molecular weight is 16Kd and 18Kd by sodium dodecyl sulfate-PAGE, respectively. These have been shown to inhibit the differentiation of myoblasts. When the growth factors are reduced artificially within culture medium containing exponentially growing myoblasts, cells initiate a differentiation program, express muscle-specific proteins after 7-8h, and begin fusion after 1d. These growth factors serve the dual role of stimulating proliferation and inhibiting terminal differentiation.