This is a revised edition of a classic and highly regarded book, first published in 1981, describing the status of theory and experiment in general relativity. This book offers a comprehensive survey of the intensive research and testing of general relativity that has been conducted over the past three decades. As a foundation for this survey, the book first introduces the important principles of gravitation theory, developing the mathematical formalism that is necessary to carry out specific computations so that theoretical predictions can be compared with experimental findings. It provides an up-to-date survey of experimental results, not only for Einstein's "classical" tests, such as deflection of light and the perihelion of Mercury, but also for new solar-system tests, never envisioned by Einstein, that make use of the high-precision space and laboratory technologies of today. The book goes on to explore new arenas for testing gravitation theory in black holes, neutron stars, gravitational waves and cosmology. Included is a systematic account of the remarkable "binary pulsar" PSR 1913+16, which has yielded precise confirmation of the existence of gravitational waves. A new chapter has been added to cover recent important experimental tests, and the bibliography has been brought up to date.