These proceedings contain the papers presented at the 4th International S- posium on Location and Context Awareness (LoCA) during May 7–8, 2009 in Tokyo,Japan.Locationandcontextawarenessarefundamentstonext-generation mobile and pervasive computing systems. Pervasive computing is a model of computing in which computation is everywhere and computer functions are - tegrated into everything. The ultimate aim is to make information, applications and services available anywhere and at anytime in the human environment in a ?uid manner appropriate to our current context. Once away from the desktop, we ?nd ourselves in a wide variety of contexts and hence situations. For computing to be relevant and useful in these emerging situations we must rely on a range of contextual cues. Context includes phys- logical, environmental, and computational data, whether sensed or inferred. In addition, context includes details of a user activities, goals, abilities, pref- ences, a?ordances, and surroundings. With location and context awareness we can expect computers to deliver information, services, and entertainment in a way that maximizes convenience and minimizes intrusion.