Mobile services have gained in importance for their ability to be consumed by mobile users regardless of their location. Mobile consumers are exposed to a large pool of services such as location-based applications, medical information, financial management, investments, and more. However, mobile service discovery needs further research to efficiently and effectively support mobility-related constraints such as availability, heterogeneity, and resource constrained devices. In this chapter, the authors define several criteria relating to mobile service discovery and categorize state-of-the-art service discovery approaches according to those criteria while paying particular attention to architectural choices, service description, and service discovery using semantic and reasoning techniques. The authors evaluate the approaches to identify their advantages and shortcomings and propose guidelines for future research for service discovery in mobile environments.