[Emergence of a new medical speciality: the example of radiology].

The example of electro-radiology in France shows that various factors influence the development of a new specialty. New technology requires the existence of professionals trained in its use for diseases affecting numerous patients. Use of the techniques generates knowledge which must be gathered and transmitted. This evolution also depends on a favourable social and medical context. The action of individuals may also play a decisive role. Finally, over time, these influences may lead to consolidation of, or new divisions in, the specialty.