This paper describes a system that facilitates and encourages the sharing of knowledge among groups of users within or across organizations. KSE (Knowledge Sharing Environment) is a system of information agents for organizing, summarizing, and sharing knowledge from a number of sources, including the World Wide Web, an organization's internal intranet, or other users. Users are organized into closed user groups or communities of interest with related or overlapping interests, such as members of a project team, students studying the same subject (perhaps at different institutions), or members of an organizational department. As well as sharing explicit (codified) knowledge, sharing of tacit knowledge is encouraged via automatic suggestion of and support for contact between people with mutual concerns or interests. Following a brief discussion of storing and organizing knowledge in KSE, the paper focuses on the following topics related to tacit and explicit knowledge in KSE: (1) ways that KSE facilitates access to and automatic sharing of explicit knowledge, including e-mail notification, keyword retrieval, a "What's new?" feature, and interest groups; (2) adaptive agents; and (3) finding people and tacit knowledge, i.e., the social aspects of the system. Two figures present a typical KSE home page and the main features of the KSE. (Author/AEF)