Previous studies have shown that radiolabelled epidermal growth factor (EGF) binds to epidermis and cornea in rats, and that topically applied EGF produces an accelerated hyperplastic epithelial healing response in scarified corneas, but has no effect on the morphology of undamaged corneas of adult rabbits. The present study was designed to determine whether systemically administered EGF modifies the morphological development of the eyelids and corneas of neonatal mice. It was found that EGF-treated mice had premature eyelid separation with advanced keratinization at the eyelid margin. The overall thickness of the cornea was less in mice given EGF, the substantia propria being principally affected. By contrast, the corneal epithelium was significantly thicker in EGF-treated mice. It was concluded that EGF affects both the substantia propria of the cornea and the corneal epithelium in neonatal mice, and that this substance perhaps plays a role in the normal development of these tissues.