Abstract: The confrontation between general relativity (and its theoretically most plausible deviations) and experimental or observational results is summarized. Some discussion is devoted to the various methodologies used in confronting theory and experiment. Both weak-field (solar system) and strong-field (binary pulsar) tests are discussed in detail. A special discussion is devoted to the cosmology of moduli fields, i.e. scalar fields having only gravitational-strength couplings to matter.