A large number of experiments in recent years have manipulated incentives in telephone and face-to-face surveys, complementing the earlier, and even more voluminous, research literature on the effects of incentives in mail surveys. These experiments are based loosely on various forms of exchange theory (e.g. Adams, 1965; Berger et al., 1972; Homans, 1961, 1974), though many are quite atheoretical. This chapter synthesizes findings about the effects of incentives from both interviewer-mediated and mail surveys in order to increase their usefulness for practicing survey researchers and to stimulate more targeted research by survey methodologists. It reviews what is known about the intended effects of incentives on response rates in both types of surveys, drawing on two existing meta analyses (Church, 1993; Singer et al., 1999) as well as on subsequent work by the same and other authors. It also reviews what is known about such unintended consequences of incentives as effects on response quality and sample composition, concerns about equity, and the development of expectation effects (Groves et al., 1999; Singer, Groves, and Corning, 1999; Singer, Van Hoewyk, and Maher, 1998, 2000). Finally, it discusses issues of cost effectiveness and suggests avenues of further research. Because of the additional complexities introduced in organizational surveys, they are not included in the present review.