Modulational Interactions in Plasmas is the first book to present all the basic considerations relevant to the topic. It adopts a simple and universal approach, based on new methods developed for the description of modulation interactions in arbitrary media. Emphasis is given to the role of modulational interactions in fundamental topics, such as laser acceleration, the generation of strong magnetic fields, r.f. plasma heating and current drive, physical phenomena in active geophysical and space experiments, interactions of r.f. radiation with the ionosphere, etc. The methods employed can also be applied to other areas of physics. Audience: Researchers in plasma and laser physics, and nonlinear optics.