These books grew out of the perception that a number of important conceptual and theoretical advances in research on small group behavior had developed in recent years, but were scattered in rather fragmentary fashion across a diverse literature. Thus, it seemed useful to encourage the formulation of summary accounts. A conference was held in Hamburg with the aim of not only encouraging such developments, but also encouraging the integration of theoretical approaches where possible. These two volumes are the result. Current research on small groups falls roughly into two moderately broad categories, and this classification is reflected in the two books. Volume I addresses theoretical problems associated with the consensual action of task-oriented small groups, whereas Volume II focuses on interpersonal relations and social processes within such groups. The two volumes differ somewhat in that the conceptual work of Volume I tends to address rather strictly defined problems of consensual action, some approaches tending to the axiomatic, whereas the conceptual work described in Volume II is generally less formal and rather general in focus. However, both volumes represent current conceptual work in small group research and can claim to have achieved the original purpose of up-to-date conceptual summaries of progress on new theoretical work.