The basic properties of gravitational radiation, as predicted by general relativity, are described and compared with those of electromagnetic radiation. Some recent results on radiative processes in the vicinity of black holes are outlined. It is stressed that some of these processes lead to more efficient methods of converting rest mass into radiative energy than any other known process except matter-antimatter annihilation. Since one would expect tliere to be a large number of black holes in the universe, these conversion processes may be important in astronomy. Research into gravitational radiation, both theoretical and observational, should therefore be conducted vigorously.