Short message service (SMS) surveys are fast, inexpensive, and increasingly common. However, there is limited research on this new mode. Using an experimental design, we conducted general population SMS surveys in Ghana, Kenya, Nigeria, and Uganda. This article (1) reports the levels and components of nonresponse; (2) evaluates the representativeness of SMS surveys relative to benchmark data; and (3) explores strategies to improve representativeness. We find that SMS surveys underrepresent women, older people, those with less education, and less technologically savvy people. Sending reminders improved representativeness, but offering shorter surveys or higher incentives did not. We conclude that presently, general population SMS surveys cannot replace face-to-face surveys. Our article provides practical guidance for survey designers and directions for future research.