This study meta-analyzes thirty-nine study results published within last ten years that directly compared Web and mail survey modes. Although considerable variation exists across the studies, the authors' findings show that mail surveys have higher response rates than Web surveys in general. Two study features (i.e., population types and follow-up reminders) are shown to contribute statistically to the variation of response rate differences between Web and paper surveys in the comparative studies. College respondents appear to be more responsive to Web surveys, while some other respondents (e.g., medical doctors, school teachers, and general consumers) appear to prefer traditional mail surveys. Follow-up reminders appear to be less effective for Web survey respondents than for mail survey respondents. Other study features (i.e., implementation of random assignment of survey respondents, incentives, and publication year) are not statistically useful in accounting for the variation of response rate differences between Web and mail surveys.