Radiology, the youngest of the major medical sciences, has undergone an extraordinary technical evolution since the discovery of X-rays. It began with the development of the different types of tomography and the adoption of many contrast agents, then proceeded rapidly to serioscopy, subtraction of images, direct enlargement, echography, thermography, and xerography. Today, even before all these innovations have come into common use, another branch of radiologic technology has evolved: computerized (axial) tomography. More than just an innovation, its true dimensions are unfore seeable. Radiology has become in less than a century an indispensable adjunct to the practice of medicine. The development of radiology as a speciality followed its technical advances, which varied greatly from country to country. This rapid development led quickly to subspecialization, even the very early development of radiotherapy and radiodiagnostics as separate entities. However, the entry of radiology into the university has preserved it a single branch of medicine, avoiding the frequent tendency toward auto nomy of the branches of a speciality. Today the fourth generation of radiologists is faced with another deci sion: whether to become technologists subjugated to their machinery, to become sub specialists with a single skill, or to remain doctors. The vast majority of this fourth generation has rejected becoming an accessory to a master technique and rather has specialized according to the hippocratic concept of medicine."