The volume ‘Medical Radiological Physics’ is intended to provide the scientific basis of diagnostics and therapy in medical radiology. The present Subvolume A reviews radiation (both ionising and non-ionising) and its biological effects, dosimetry in diagnostic radiology and radiotherapy, as well as in nuclear medical diagnostics and therapy, and, finally, medical radiological protection relevant for patients, personnel and the general public. Not only fundamentals but also basic data pertinent to the topics dealt with have been collected by numerous experts of great international renown.