This 1985 text offers a comprehensive survey of research and testing conducted in general relativity. As background it introduces the important principles of gravitational theory and develops the mathematical formalism necessary to carry out specific computations in order to compare theoretical predictions with experimental findings. The survey of experimental results includes not only Einstein's classical tests but also solar-system tests, never envisioned by Einstein, that make use of the high-precision space technology of the 1960s and 1970s. It also gives a systematic account of the remarkable 'binar pulsar' PSP 1913 16, the first evidence of gravitational waves. This volume will be a useful point of reference for any reader interested in the empirical underpinnings of one of the great theories of the twentieth century.