A collaborative effort has been formed to search for gravitational waves from sources in and beyond the Milky Way galaxy and to pinpoint the source of the signals. The waves were predicted by Albert Einstein in 1916 but have not been directly observed. The collaboration will link data from three Laser Interferometer Gravitational-Wave Observatory (LIGO) detectors in the US, from the GEO600 German-British interferometer project in Schäferberg, Germany, and from the Virgo interferometric gravitational-wave detector at the European Gravitational Observatory in Cascina, Italy.The agreement calls for data sharing to begin when the sensitivity and the duty cycle of the interferometers allow a significant contribution to joint searches for the waves. The Virgo collaboration comprises scientists from institutions in France, Italy and the Netherlands. The LIGO Scientific Collaboration includes members of the GEO600 project. LIGO is operated by California Institute of Technology in Pasadena and MIT in Cambridge, Mass.