Unlike any other wound care device or pharmaceutical, medicinal maggots convey multiple therapeutic benefits at the same time when applied to chronic and/or infected wounds. In addition to providing an ideal healing environment through debridement and infection control, maggot excretions and secretions actively promote wound healing through a wide range of specific physiological mechanisms and pathways. After a brief review of early studies into the healing properties of medicinal maggots, and what is known from randomised clinical trials, the chapter explains in detail the biochemical and physiological principles of maggot-mediated wound healing.