Providing the latest developments in the application of electromagnetic methods, this title is a revised edition of the book "Frequency and Transient Soundings" by A.A. Kaufman and G.V. Keller published in 1983. In this volume the physical principles, theory and interpretation of electromagnetic soundings and profiling are developed and explained. The authors systematically derive the relationships between components of electromagnetic fields measured, transmitter-receiver separations and frequency spectrum on the one hand, and parameters of geoelectric sections on the other hand. In addition you will find case histories illustrating the applications of modern instruments for electromagnetic soundings and profiling in agricultural and geotechnical engineering, environmental site assessments and ground water investigations.