A pressure ulcer is any lesion caused by unrelieved pressure that results in damage to the underlying tissue.1 This short and simplistic definition belies the complexity and significance of this type of wound. Pressure ulcers have a major impact on the health care system, wound care providers, and, most especially, patients and their families. Understanding of the pathophysiology of pressure ulcers is evolving as research advances in the areas of basic cellular mechanisms and clinical practice. It is hoped that this enhanced knowledge will improve wound care practitioners' ability to diagnose and treat pressure ulcers and, more importantly, identify at-risk patients to prevent pressure ulcers from developing in the first place.