The purpose of this research is to examine cultural difference in Turkish and American preschoolers' play, aggression and victimization behaviours. The research has been performed in a nursery school affiliated to a university in one of the big cities of Turkey and in two nursery schools affiliated to a university in one of the Northern states of the United States of America. It was composed of 55 Turkish children, 36-72 months old, (29 girls, 26 boys) and 50 American children, 36-72 months old, (32 boys, 18 girls), totally 105 children (61 boys, 44 girls). Observations and teacher report were used in this study. According to the results; Turkish children showed more physical and relational aggression and victimized more than American children. American children showed parallel play more than Turkish children, and Turkish children engaged in pretend play more than American children. Surprisingly, the most interesting result; social pretend play is predicted observed and teacher reported relational aggression in both cultures. (author abstract)