Dynamic light scattering is a new method for investigating macromolecular systems. The importance of the technique lies in its non-invasive character. It can be employed on extremely small fluid volumes, the instrumentation is relatively inexpensive and allows the rapid determination of diffusion coefficients as well as providing information on relaxation time distributions for the macromolecular components of complex systems.This volume is directed in part to the philosophy and current practice in dynamic light scattering: single photon correlation techniques are introduced, a discussion of noise on photon correlation functions is given and data analysis in dynamic light scattering to polymer structure analysis is presented and a comprehensive introduction to diffusing wave spectroscopy is given. Theoretical developments relating dynamic light scattering to the viscoelasticity of polymers in solution and in the bulk are described. The second aim is to illustrate the widely varying fields in which the technique finds application. Chapters are to be found on multicomponent mixtures, polyelectrolytes, dense polymer systems, gels, rigid rods, micellar systems and the application of dynamic light scattering to biological systems.