This book is written for the biochemist, biophysicist or cell biologist, who is interested in applying Resonance Energy Transfer to study proteins, membranes and other biological systems. It is a handbook that provides a wealth of information an Förster distances, quantum yields and other spectroscopic parameters, and can, therefore, assist in choosing the Donor-Acceptor pairs that are most suitable for tackling the problem at hand. The book also gives a clear and virtually complete overview of the theory including limits on the orientation factor, effects of motion on transfer, concentration depolarization, and limitations of the technique. It contains a large number of tables and diagrams, is accessible to the beginning graduate student and is suitable as a supplementary text for courses on biophysical techniques.