This volume contains the lectures and seminars presented at the NATO Advanced Study Institute on Lasers in Biology and Medicine organized by the International School of Quantum Electronics at the Villa Le Pianore, Camaiore, Italy, August 19-31, 1979. Most laser applications in biology and medicine are highly interdisciplinary in nature, drawing from and pertaining to such diverse fields as the physical sciences ( (bio)physics, (bio)chemi­ stry) , engineering, the biological sciences (cellular research, photobiology) and finally theoretical and clinical medicine. Indeed the group of participants of the summer school did reflect this diversity both in background and interest. The presentations con­ tained in this volume mainly fall into two categories: tutorial lectures on the most important general subjects, intended to lay a common base for all participants, and a number of more advanced con­ tributions, serving the purpose of exemplifying selected but typical applications in their current state of development. Intense inter­ communication, lively discussion, and here and there even future cooperation were the general aims more than a detailed in-depth discussion of one or the other aspect of this large field. In this sense it is the hope of the organizing committee that, despite the inevitable limitations, a broad and reasonably representative cov­ erage of the field has been achieved and that this volume may be a valuable aid for newcomers to get a good start into this complex subject area for some years to corne.