The rapidly changing technological landscape of the United States has important implications for survey researchers. The challenges are well known for outbound telephone surveys, but to a lesser degree for Web-based surveys. According to estimates by the Pew Internet and American Life project, 55% of cellphone owners access the Internet via their phone, and for many Americans a cellular device is their only Internet connection. Mobile devices provide instant connectivity, allowing respondents to take surveys at any time of day, no matter where they are located, which is an exciting prospect. However, very little research exists to date about surveys completed via smartphones and other mobile devices. It is unknown if surveys designed to be compatible with mobile Web browsers increase response rates, or if respondents who respond via a mobile browser are demographically different than desktop respondents. Further, it is unknown if best practices for the design of desktop based Web surveys translate to mobile based surveys. The present study was conducted using the Gallup Panel, a probability based panel of over 50,000 members who complete studies via the Web, mail, or telephone. Panel members were randomly assigned to one of 12 treatment groups that compare three different modes (traditional Web only, traditional Web plus mobile browser compatible and outbound), two treatment for length, and two treatments for question layout. Closed and open-ended questions were tested. Paradata, such as user agent string, time per survey, breakoffs, and answer changes, were also recorded as part of the study. The results will be analyzed to better understand how mobile compatible surveys affect response rates, the representativeness of the sample, and data quality. The authors will draw conclusions about the costs and benefits of mobile compatible surveys, and make suggestions for best practices.