The historical outline shows the development of radiologic diagnostics from the early Roentgen days up to this centenary. The roots of radiologic diagnostics go back to the European Renaissance. It is a history of medical pattern recognition and functional analysis by several methods including X-rays, ultrasound waves or strong magnetic fields. The difference between conventional radiographs and a picture reconstructed after digitalization, with several possibilities of postprocessing, is explained. Research and further technical revolutions, like the development of semiconductor elements and computers or tailored contrast media, sophisticated pictorial representations and perceptions, are among the cornerstones of imaging diagnostics. During this century many diseases have changed their manifestation and spread. This is illustrated by tuberculosis and cancer and highlights the growing importance of imaging diagnostics and interventional radiology. The thorny path to independence of radiology is also a history of the medical establishment's resistance.