Originally published in 1980, this book examines the effects of ultraviolet radiation on the genetic material of cells and the repair mechanisms by which many cells can reverse the damage caused by UV. The work was intended to be a combination textbook/introductory monograph for graduate and advanced undergraduate students in photobiology, biophysics, microbiology, and genetics. It was the first volume in an introductory series on topics in biophysics sponsored by the International Union of Pure and Applied Biophysics.