This paper describes the results of a field test of a redesigned monthly customer satisfaction measurement questionnaire for the largest business customers of a national package shipping company. In response to a desire to allow these large business customers to provide their feedback via the Web using a mixed-mode design, Gallup conducted a field test experiment to measure response differences between CATI and web versions of the survey. One concern in multiple-mode studies is that the method of data collection can affect the distribution of responses. Recent studies suggest that when a scale is visually presented (as in a Web survey), respondents are more likely to choose the middle alternatives, than when it is exclusively oral (as in CATI) (see Dillman, et al, 2000). Thus a main research question was whether the introduction of a Web option would tend to reduce the proportions of responses in the most favorable and least favorable categories (using a Likert scale). In a customer satisfaction survey, this shift could have significant effects on assessment of the organization or company. The design of the field test allowed us to test this and other hypotheses about mode effects. · What mode effects, if any, were observed in the data? · What are respondents' preferences with respect to mode of survey administration? · What mode differences were observed in response rates, breakoff rates, and survey length? Results of the field test indicate no consistent mode effects on favorability (top 2 box scores) towards the company's products and services. However, web responses are significantly more likely to be clustered in the middle categories than CATI responses, which tend to be more extreme. Thus, inclusion of the Web option would tend to decrease the percentages of most favorable and least favorable responses.