Epidermal Growth Factor (EGF) is a small growth factor containing 53 amino acid residues capable of stimulating the proliferation of both mesenchymal and epithelial cells. EGF and FGF-2 induce the proliferation of neural precursor cells isolated from specific regions of the embryonic and adult brain. Biological activities ascribed to EGF include epithelial development, angiogenesis, inhibition of gastric acid secretion, fibroblast proliferation, and colony formation of epidermal cells in culture.