This article deals with research which attempts to demonstrate the value of health care delivered via telemedicine. A great variety of telemedicine services have been proposed. Much of the published work concentrates on the power of the technology and the content and quality of interaction it supports. There are other parameters to be considered in assessing telemedicine as a component of a health-care system, parameters which in practice determine the nature of the service being provided. Despite the fact that much work in telemedicine is published as short accounts of pilot projects, there is little research that explicitly addresses the difficulties involved in setting up new telemedicine services. Some studies have been performed which attempt to evaluate telemedicine services, but relatively few studies have been able to collect the data required to provide an unambiguous demonstration of their value.