Location based service (LBS) is emerging as a killer application in mobile data services thanks to the rapid development in wireless communication and location positioning technologies. Users with location-aware wireless devices can query about their surroundings (e.g., finding the nearest Japanese restaurant or all shopping malls within 5 miles) at any place, anytime. While this ubiquitous computing paradigm brings great convenience for information access, the constraints of mobile environments, the spatial property of location-dependent data, and the mobility of mobile users pose a great challenge for the provision of location-based services to mobile users. This seminar will provide an overview of research issues arising from accessing of location-based services in a mobile computing environment and discuss the state-of-theart solutions. In particular, it will focus the discussions on the following topic areas: 1) location positioning technologies; 2) query processing; 3) cache management; and 4) privacy and security.