The spreading of cells across the surface of an epidermal wound enables epidermal migration to be studied independently of the wound contraction that occurs in deeper wounds. In particular, the stimulus for the increase in epidermal mitosis during would healing is uncertain. Our modelling suggests that biochemical regulation of mitosis is fundamental to the process, and that a single chemical with a simple regulatory effect can account for the healing of circular epidermal wounds. The model results compare well with experimental data.