A new paradigm for computer-supported cooperative work and a research agenda for developing and testing this paradigm are proposed. The book outlines a comprehensive model of collaboration that integrates the cognitive/conceptual and social dynamics of groups. The challenge faced by all groups engaged in intellectual work is to divide the task so that efforts of individual members may proceed in parallel and, on the other hand, to synthesize their separate contributions to form a coherent whole. These challenges are addressed through an examination of the general form of a theory of computer-based collaboration that extends across different tasks and situations. Two metacognitive issues--awareness and control--are discussed as arising in collaborative behavior. A number of advanced computer systems that support collaboration are reviewed; their impact on the thinking and behavior of groups is a particular focus. The theoretical framework combines elements of Information Processing System (IPS) theory, and its detailed process models of cognitive behavior, with the situated perspective of activity theory. The book suggests new ways of conceiving problems and solutions to all those interested in the ways in which people interact with each other and with computers to achieve goals. (Contains 97 references.) (Author/MAS)