  A world-wide effort is now underway to build gravitational wave detectors
based on highly-sensitive laser interferometers. When data from detectors at
different sites is properly combined, it will permit highly-sensitive searches
for a stochastic background of relic gravitational radiation. These lectures
(from the Les Houches School in October 1995) review the current status of this
program, and discuss the methods by which data from different detectors can be
used to make measurements of, or place limits on, a stochastic background. They
also review possible cosmological sources and their potential detectability.
