The need for major surgery involving bone and skin grafting procedures in the treatment of severe alveolar atrophy has, for many patients, been obviated by the advent of reliable endosseous implant systems. However, some patients, usually for medical, psychological, or financial reasons are unsuitable for endosseous implant therapy. In such patients, ridge augmentation with particulate hydroxyapatite may result in significantly improved denture function. However, hydroxyapatite tends to disseminate throughout any surgically created subperiosteal space, resulting in an undesirable ridge form. This problem may be overcome by the use of tissue expanders in a two-stage surgical procedure. This article briefly reviews the concept of tissue expansion and describes its application to the technique of alveolar ridge augmentation. (Implant Dent 1992;1:177-181)