The advances in wireless communications and mobile devices have resulted in a massive growth of the video services over mobile networks. In this article, we study the potential of peer-assisted video delivery in WiFi mobile networks aimed at reducing servers¿ load. Our study is based on a real measurement of mobile video viewing logs from a leading Internet video provider for 14 days. We analyze viewing behavior of users with respect to three main factors for the design of peer-assisted delivery network: viewing time, user population, and user locality. We then discuss the implications of the observations. Finally, we apply the findings on a BitTorrent-like VoD system and perform experiments with the collected viewing logs to demonstrate the benefits of peer-assisted video delivery. The peer assistance can reduce the servers¿ load by as much as 50 percent for popular videos on average.