Wound healing is part of the normal general repair process of the body. Its efficient completion depends on many factors, some physical, eg, pH, oxygen tension and tissue tension, and some biological, eg, cell-cell interaction and feedback of extracellular matrix on to the cells which produce it. The factors which affect healing are discussed and failures and anomalies in the process described. New techniques which may improve the quality of healing in specialised tissues are explained. Recent research on wound healing has concentrated on the role of the different cell types in the process and also on the effects of micro-environment on the enhancement or inhibition of cellular activity. The wound is a situation in which cells are apparently operating at the limits of their powers of survival and very slight modification of the micro-environment can render the tissue either unduly hostile to the cell or can enhance cellular activity. While it is not possible to increase the rate of healing of a clean surgical wound to any useful degree, an understanding of the mechanics of wound healing is essential to a rational treatment of simple or indolent wounds. It is especially important that surgical or medical treatment should complement, rather than compete with, the natural process. Tight bandages, which compress circulation, or excessive washing, which may remove macrophages and dilute bacteriostatic or chemotaxic agents, should be avoided.