The three studies involved attempt to assess the nature of cooperative and competitive behavior of young children in different socioeconomic classes. In the first study, 36 pairs of Head Start children, representing Mexican-American, Negro and Caucasian ethnic groups, were investigated concerning their cooperative-competitive behavior in relation to their ethnic differences. Variances in behavior were marked from group to group. The second study involved 240 children, half of whom were enrolled in Head Start. The above three ethnic groups were represented equally in this project. Ethnic background was found to affect competitive behavior in only a partial way; it related to sex. Mexican-American boys were less competitive than other groups. The third study compared cooperative-competitive behavior in kibbutz and urban children in Israel, using 40 kibbutz children and the same number of city children, both with an age mean of eight years. Kibbutz children showed more cooperative behavior than did the city children. (MK)