This study develops an action research approach to the investigation of children's games and sports activities. Eight hypotheses concerning the differential effects of participation in organized sports and participation in child-directed games are generated from a review of theory and research. Hypothesis 1 postulates that participation in organized sports will be negatively related to participation in child-directed games. Additional hypotheses probe the relation of game and sport participation to prosocial behavior, self-esteem, persistency, tolerance for ambiguity, locus of control, machiavellianism, and creativity. Several instruments were developed and modified for data collection among a sample of 170 male and 174 female subjects in 3 elementary schools. Analysis of variance, correlation and regression techniques were used to analyze the data. Hypothesis 1 was not supported. Three additional hypotheses received no support, while 4 of the hypotheses received either partial or moderate support within age-sex sub-sets of the sample. A follow-up study of the effect of sports participation on personality development found a tendency for nonparticipating females to become less machiavellian. Conclusions as well as implications for research and practice are advanced. (RH)