While sensor networks provide the opportunity for sophisticated, context-aware services, privacy concerns can seriously affect user acceptance and become a barrier to their long-term successful deployment. This chapter discusses privacy issues in sensor networks, by identifying the requirements for privacy preserving deployments, analysing the challenges faced when designing them, and discussing the main solutions that have been proposed. Privacy can be addressed in different levels of the network stack and at different points of the information flow. The privacy requirements and the mechanisms that address them are categorised into privacy sensitive information gathering schemes, controlled information disclosure approaches, and mechanisms for the protection of the communications context. The separate discussion of the approaches highlights the diverse privacy aspects that they are focused on, and shows how the approaches can be viewed as complementary to fulfill the complete spectrum of sensor networks' privacy needs.