A study of the effects of peer-pairing and integrative motivation on both formal language performance and actual language behavior with Korean immigrant children is presented. The formal language learning was measured by tests of oral production and listening comprehension, and actual language behavior was measured by observations in a natural school environment. Both oral production and listening comprehension posttests were administered four-and-a-half months after pretest administration. Thirty elementary school children (11 boys and 19 girls) were randomly assigned to two groups, resulting in 14 children (8 girls and 6 boys) in the peer-paired group and 16 (11 girls and 5 boys) in the no-paired group. Stepwise multiple regression analyses indicated that (1) peer-pairing was a significant predictor for listening comprehension and the actual language behavior, and (2) prior language knowledge was the best predictor of formal language learning. The theoretical implications are that peer-pairing not only facilitates formal listening comprehension and actual language behavior, but also enhances social relationships between second-language learners and the target-language speakers. (MSE)