The proliferation of cell phones has led to an ever increasing number of inappropriate interruptions. Context-aware telephony applications, in which callers are provided with context information about the receivers, has been proposed as a solution for this problem. This approach, however, raises many privacy issues that may render it infeasible. In this paper, we report on an in-situ study of user privacy preferences and patterns of sharing different types of context information with different social relations. We found that participants disclosed their context information generously, suggesting that context-aware telephony is not only feasible, but also desirable. Our data shows a distinct sharing pattern across social relations and different types of context information. We discuss the implications of the results for designers of context-aware telephony in particular and contextaware applications in general. Categories and Subject Descriptors H.5.2 User Interfaces- user-centered des...