IAU S261 summarizes the present state of applied relativity, and discusses the applications and future tests of general relativity.

Preface; 1. Astronomical space-time reference frames; 2. Astronomical constants, nomenclature and units of measurement; 3. Time scales, clock and time transfer; 4. Equations of motion of astronomical bodies and light rays; 5. Motion of astronomical bodies; 6. Experimental foundations of general relativity; 7. Pulsar timing; 8. Astrometric and timing signatures of gravitational lensing and gravity waves; 9. Astrometric and timing signatures of galactic and extragalactic black holes; 10. Astrometry and ground-based interferometry; 11. Promises and challenges of Gaia; 12. Future high-accuracy projects; 13. Future prospects of testing general relativity; Author index; Subject index; Object index.