This research process and performance consequences of changes in various aspects of work groups. It builds upon and is an extension of a continuing program of research on time in group interaction and performance. The studies will make use of two major products of earlier work in that program: A theory of work in groups (called Time, Interaction and Performance, of TIP, theory), and a time-oriented system for analysis of interaction process in work groups (called Time-by-Event-by-Member Pattern Observation system, or TEMPO). TIP theory predicts a number of important consequences for group process and outcomes, of changes in group membership, changes in group tasks, and changes in the circumstances under which the group is operating. TEMPO provides a method for testing many of the predictions about process changes. A new set of techniques, called "process replay", will be developed and used to explore the situated meanings of acts within group process and relate those meanings to the main concepts of TIP theory.