The aim of this study is the investigation and clarification of the socializing function of play as a natural source of social experience and as an intermediary of social contacts. The principal point of attention is the question of developing social relationships and attitudes of children while they play. The study deals with some problems of the social behaviour of children at pre- -school age and some typical forms of behaviour in this age-group. The substance of the work consists in an analysis of games (i. e. creative and motional games) in nursery schools and kindergartens. The primary aim of the research was to find out the influence of the rules of the game and the rules of behaviour in the game on developing and regulating social relationships, and then to find out and describe the factors which interfere with the game and consequently with the social relationships of the children; the influence of the structure of the children’s group on the relationships of the children was partly registered, and finally the role of the teacher in moulding relationships was made clear. The research was carried out in 16 departments of nursery schools and kindergartens, involving 486 children of different age categories. 1215 games were recorded and analysed, 807 of which were creative and 408 motional games. The study concludes by confirming, precisely and concretely formulating the hypothesis that play offers ample opportunities for initiating and developing social relationships and that, through its intermediary, part in common activities, and finally, that the child learn to co-operate and take the child acquires various manners of social behaviour. The study aims an enriching the theory and practice of preschool education and therefore the pedagogical application of the facts found out is also dealt with. The facts arrived at by the research can be applied in the moral education of children, in training the habits of social behaviour and also in the teacher’s role in methodologically directing the games and using situations in the games to train the children in social relationships.