Abstract-As the mobile platform pervades human life, much research in recent years has focused on improving the reliability of mobile applications on this platform, for example by applying automatic testing. However, researchers have primarily considered testing of single version of mobile applications. Although regression testing has been extensively studied for desktop applications, and many efficient and effective approaches have been proposed, these approaches cannot be directly applied to mobile applications. We first present a bug study on real-world Android bugs to show the existence of regression bugs, which motivates the need for an efficient regression test selection technique for Android applications. Next, we introduce Redroid, a new approach to regression test selection for Android applications. Our approach leverages the combination of static impact analysis and dynamic code coverage, and identifies a subset of test cases for reexecution on the modified application version. We implement our approach for Android applications, and demonstrate its efficacy through an extensive empirical study.