The mobile revolution has transformed the lives of Kenyans, providing not just communications but also basic financial access in the form of phone-based money transfer and storage, led by the M-PESA system introduced in 2007. Currently, 93 percent of Kenyans are mobile phone users and 73 percent are mobile money customers. Additionally, 23 percent use mobile money at least once a day. New potential for mobile money has come with the rise of interest-earning bank-integrated mobile savings systems, beginning with the launch of the M-KESHO system in March 2010. The authors examine the mobile savings phenomenon, using data collected in a special survey in late 2010. They show that the usage of bank-integrated mobile savings systems like M-KESHO remains limited and largely restricted to better-off Kenyans. However, what the authors term "basic mobile savings" -- the use of simple mobile money systems as a repository for funds -- is widespread, including among those who are otherwise unlikely to have any savings. Holding other characteristics constant, those who are registered for M-PESA are 32 percent more likely to report having some savings.