The degree to which children of 2 age groups and different subcultures differ in the amount of cooperative and competitive behavior they exhibit is explored. A game measuring cooperation and competition was played with pairs of Anglo Americans and Mexican Americans who were 4-5 years of age and with Anglo Americans, Mexican Americans, and Mexicans who were 7-9 years old. Cooperative play allowed both pair members to receive rewards; competitive play was irrational, allowing no subject to reach his goal. The number of moves pairs took to reach a goal indicated that younger subjects were more cooperative than older subjects. Among the older children, Mexicans were most cooperative, Mexican Americans next, and Anglo Americans least cooperative. Also among the older children, instructional sets designed to create "I" orientation increased competition whereas sets stressing "we" orientation increased cooperation. Qualitative differences between patterns of play were noted for the cultural and age groups. Sex differences were not found. A list of references, footnotes, 2 tables, and 1 paradigm are also presented. (AL)