Results are described from four epidemiologic studies in the United States which used random digit dialing in over 30,000 households to identify controls from the general population for use in case-control studies. Methods and problems in telephone sampling are discussed. It is concluded that if complete population rosters are unavailable and if the population to be sampled has the high rates of telephone ownership typical of much of the United States, telephone-based sampling can yield a nearly random sample of the individuals in a population, often at much less expense than can dwelling-based sampling.