Studies in group dynamics in Japan, which started just after the Second World War, are reviewed. This review categorizes the studies into two classes: those conducted in the first generation (up to the 1970s) which still remain influential today, and those which represent the current major research trends in the area. The first generation is characterized by a strenuous catching up of studies conducted in the U.S. The second generation has been a theoretical and empirical expansion of the area, and has emphasized the bilateral, dynamic relations between the nature of human collectivities (including culture) and the individuals' psychological state. It has been increasingly recognized that what was regarded as an individual psychological phenomenon in the past should be re-examined from the viewpoint of group dynamics. This goes beyond the traditional definition of small groups research in the laboratory setting. Group dynamics is developing as a field of study in which any kind and size of human collectivity is investigated regarding its dynamic nature and functions that provide a life-world appearing in front of each individual in the collectivity.During the half-century since the Second World War, group dynamics in Japan have taken a course similar to that of the Japanese economy. The first half of this course was devoted to the intensive learning from and the strenuous catching up of the Western countries, mainly the U.S. The second half, beginning in the 1980s, has been characterized by an increasing emphasis on originality and creativity in our own research activities. This paper will review both the works that were carried out in the first half of this period, which still contribute to current research in various ways, and the work that has emerged since the 1980s, which continues to advance further this area.In this paper, group dynamics is defined as a field of study in which the dynamic nature of human collectivities or groups is investigated by examining the collectivities as wholes on the one hand, and the dynamic bilateral relations between the collectivity and the lives, or the psychological states, of the individuals who belong to these collectivities on the other. It should be stressed here that group dynamics defined as such is not restricted to studies of small groups in laboratory settings, which is likely to be assumed by many people. Such an expansion of the research frontier beyond traditional group dynamics is a result of attempts by researchers in the current scene of group dynamics in Japan (e.g., Sugiman, 1997).