Epidermal growth factor (EGF) receptor hyperstimulation induced by systemically administered EGF or by the development of transgenic mice overexpressing transforming growth factor alpha (TGF alpha) or other EGF-related ligands is known to induce various effects, such as acceleration of developmental processes like incisor eruption, inhibition of gastric acid secretion, morphologic changes in the pancreas resembling pancreatitis, and malignancies in mammary glands and the liver. The present investigation was initiated to explore the effects of systemic EGF administration to the mature organism in a species with greater anatomic resemblance to humans than rodents.