Advances in Radiation Biology, Volume 3, reflects a continuing effort to cover a wide spectrum of radiation science in this serial publication. The book contains six chapters and opens with a review of developments of physical theory in an area of interest to biophysicists. This is followed by subsequent chapters on problem of photodynamic action, which demonstrates the role of energy transfer in radiation damage development; the sensitization of biological systems by small molecules; and problems concerned with the identification and study of the biological effects of radioactive decay. Subsequent chapters deal with a survey of human radiation cytogenetics and progress in human radiobiology.