While internet surveys garner historically lower response rates compared to other survey modes, strategic design of initial respondent contact can help boost response. Mail pre-notification letters may aid in legitimizing a mailed or internet questionnaire, however there are additional costsassociated with mailed pre-notification letters. At the same time, there are concerns about e-mailed pre-notification letters being viewed as spam, yet one may expect that an invitation in the same mode as the survey may encourage response. This methodological brief will show the results of a randomized pre-notification letter mode experiment embedded in a web survey to reveal differences in response rates and respondent characteristics between mail and e-mail pre-notification conditions. The Qualified Health Plan Enrollee Experience Survey, funded by the Centers for Medicaid and Medicare Services, gathers information on people’s experiences with the health plan they enrolled in through the Affordable Care Act’s Marketplaces. During the survey field test in 2014, 3,340 people were randomly assigned into two equal groups. One group received the pre-notification invitation by e-mail while theother received the invitation by mail with instructions to complete the survey online. All subsequent reminders were sent via e-mail. Analyses showed that the response rate was 1.4 times higher for those who received a mailed pre-notification invitation (16.0%) compared to an e-mailed invitation (11.3%). The results of this mode experiment are important to informing data collection methods for researchers considering an internet option as part of their data collection design.