In the years immediately following World War II, radioastronomers concentrated on following up on the accidental wartime discovery by British and American radar operators of radio bursts from the Sun. However, the continued push toward shorter and shorter radio wavelengths, combined with greatly increased sensitivity and angular resolution, quickly led to a series of remarkable and unexpected discoveries. Radio galaxies, quasars, pulsars, interstellar masers, gravitational lenses and the microwave background radiation—all now familiar topics of the astronomical and popular literature—were discovered serendipitously because of their radio emissions. A new generation of radiotelescopes to be built in the 1990s, together with major improvements in existing instruments, will give even further large gains in sensitivity, angular resolution and image quality, especially in the newly opened millimeter and submillimeter regions of the electromagnetic spectrum.