This article provides a summary of empirical research on groupthink theory. Groupthink research, including analyses of historical cases of poor group decision making and laboratory tests of groupthink, is reviewed. Results from these two research areas are briefly compared. Theoretical and methodological issues for future groupthink research are identified and discussed. I conclude that groupthink research has had and continues to have considerable heuristic value. A small, but growing, body of empirical literature has been generated. In addition, groupthink research has stimulated a number of theoretical ideas, most of which have yet to be tested. Copyright 1998 Academic Press.