Through an experimental study, this research note analyses the effect of incentives, announced interview length, and interviewer characteristics on response rates in a CATI-study. Survey response rates are declining throughout the developed world (De Leeuw & De Heer, 2002). A public weary of having their dinner interrupted by an increasing number of polling agencies and media-conducted surveys (not to mention other types of commercial calls) has increased refusal rates. This development is partly aggravated by the fact that more and more people increasingly rely on cell phones and unlisted numbers, which are not included in survey samples unless Random Digit Dialing (RDD) is used. Furthermore, together with the increasing number of polls conducted in recent years, there has been an increasingly louder public debate calling for a ban on polls in the weeks prior to elections (e.g. Schultz-Jorgensen, 2005; Ullerup, 2005). This public critique of commercial polling might also have increased the likelihood of potential respondents to refuse to participate in surveys. Response rates in Denmark have declined in recent decades, as has been the case in other western countries. The Danish National Institute of Social Research (SFI), one of the most respected polling agencies in Denmark, has experienced a 10 percentage point decrease in response rates over the last ten years, averaging over the 30–50 telephone and face-to-face surveys they conduct annually (personal communication with SFI, 2005). Other commercial agencies have also experienced declining response rates in recent years (personal communication with Gallup, Vilstrup, Ramboll Management 2005). Throughout the period marked by declining response rates, the polling industry has made various attempts at reversing—or at least halting—this decline. Survey research organizations have, among other things, increased the number of call-backs and advance letters, as well as introduced different forms of incentives to encourage survey participation. Much attention was paid to the declining response rates (Steeh, 1981; Smith, 1995; Curtin, Presser, & Singer, 2005) and the impact of efforts to improve them. Research indicates that advance letters and postcards improve response rates significantly and cost-effectively. Hembroff, Rusz, Rafferty, McGee, and Ehrlich (2005) reveal that advance letters improve response rates by 5.8 percentage points and postcards by 2.8