This chapter presents the main features entailed in providing location services in cellular networks. It begins by describing some of the most important location-based services and the main location techniques that have been developed in order to allow these services to be provided. These techniques involve several constraints that reduce their applicability in certain environments. Several of these restrictions are explained in this chapter, as well as the solutions proposed in order to overcome them. Regulator bodies have included some of these techniques in their official recommendations. This chapter also reviews the location architectures standardized for use in the main cellular networks and presents the concept of location middleware as a natural addition to these architectures.