Increased incidence of telephone answering machines and the use of such devices to screen calls pose a potential threat to the representativeness of samples in telephone surveys. Using data from nine statewide surveys, this analysis examines the extent to which answering machines are used to screen calls and the demographic characteristics associated with answering machine use and call screening. Results show that at most two to three percent of households use answering machines to screen calls, and that such screening is more likely to take place in households with higher family incomes, outside rural areas, and which include individuals who are younger and have higher levels of education. While call screening does not presently threaten the representativeness of samples in telephone surveys, the increased incidence of answering machines together with the increased percentage of households indicating these devices are sometimes used to screen calls demonstrate that the potential bias from this source is growing