Abstract When a tooth is moved during orthodontic treatment, changes may be observed in the surrounding gingivae. These changes may be seen superficially during routine orthodontic treatment and in study models. From study models taken each day over a period of months and from the observation of the patients at less frequent intervals, four stages of tooth movement are described: (1) prior to extraction, (2) immediately following extraction, (3) the distal movement of the tooth to the point where the epithelium separates from its mesial aspect, and (4) the production beside the mesial surface of the tooth of a red patch in the epithelium and the creasing of the epithelium on the distal aspect. The appearance of the tissue on the mesial aspect of the tooth is variable. The red patch is considered to be the reduced enamel epithelium which has peeled off the surface of the tooth.