Mankind has evolved in a sea of radiation. We have been bombarded constantly by X rays, y rays, UV rays, and particulate radiations from outer space, and by terrestrial radiations from the ground we walk on, from our building materials, and from our own bodies. Recently, we have become increasingly subjected to man-made radiations, especially from the medical and defense industries. All of these radiations are capable of affecting us biologically, both to our benefit and to our detriment. This book provides a thorough review of the physical and biological dosimetry of these radiations. It is targeted to those health professionals who are concerned with understanding the mechanisms fundamental to the biological action of ionizing radiation or who are involved in the application, measurement, or treatment of the effects of such radiations. The first chapter, on "Bioeffect Dosimetry in Radiation Therapy," should be of special interest to anyone involved in the treatment of cancer by radiation. It includes a brief review of the history of the manipulation of time-dose parameters in order to improve therapeutic benefit, and an up-to-date analysis of time-dose relationships designed for use in fractionated radiotherapy and brachytherapy. This is followed by two chapters reviewing and comparing national and international prools for the precise measurement of photon and electron radiations in therapy. These chapters should be invaluable to radiation physicists responsible for treatment machine calibrations.