Welcome to MobiSys 2013: The Eleventh International Conference on Mobile Systems, Applications, and Services. As the premier forum for presenting the latest research in mobile and wireless systems, this year's conference attracted a record number of 211 submissions, a sign of continuing vibrancy and increasing maturity of our community. In addition to the strong technical program covering virtually every major topic of mobile systems research, we've incorporated a new video program showcasing innovative ideas selected from submissions, and have continued the tradition of having an interactive demo and poster fest. The Technical Program Committee and Industrial Reviewer Panel are to be lauded for their extraordinary effort in vetting each paper with care during the rigorous review process. Each paper was assigned to three Program Committee members for a first round of reviews. Each of the 211 papers with at least one positive review (weak accept) was assigned two additional reviewers from the Program Committee in the second round. A paper with potential industrial applications was further assigned to an Industrial Reviewer Committee member. In all, the Program Committee members and industrial reviewers generated 866 reviews and the top 60 papers received at least 5 reviews. The Program Committee met for a full day at Jekyll Island, Georgia, USA. The Committee discussed the top 60 papers and accepted 33 papers for the program. Each of these 33 papers was shepherded by a member of the Program Committee, to ensure that recommendations made by the reviewers and during the Program Committee meeting were satisfactorily addressed. The resulting technical program is the fruit of labor by many. We want to thank all the authors of submitted papers. We are indebted to the Technical Program Committee and Industry Reviewer Panel for their extraordinary work in reviewing papers and providing feedback for the authors, and the Video Program Committee for reviewing and selecting the short videos. We hope you will find the program interesting and thought-provoking, and you will take this opportunity to share your ideas while also networking with other researchers and practitioners from around the world.