Incentives are known to increase response rates in mail surveys, and although they are increasingl being used in face-to-face and telephone surveys, there is much less information about their effects in those surveys, which differ radically in the demands they place on respondents. In this article, we analyze all the studies we have been able to locate that experimen with incentives in surveys done in person or by telephone in order to answer four questions: Do incentives improve response rates and does the effect vary by mode of interviewing? Are prepaid incentives more effective than promised incentives? Is money more effective than a gift? What is the effect of interview burden on the effectiveness of incentives?