An examination of the play situations in which children are successful in learning second languages was undertaken based on observations that children in foreign language settings learn languages quickly in the process of daily play activities. A wide variety of activities were examined, including play phone conversations, soccer, elastic rope jumping, card and board games, role playing, and object-based fantasy. Structural elements examined include play with minimal language, contextualized formulae, turn exchanges, gestural support, imitation, explicit instruction, role assignment, and arguments. It was found that: (1) in different types of games children appear to routinely use their activity knowledge as if there were no language barrier; (2) language use differs considerably in various activities; (3) factors seeming to facilitate learning were redundancy with action that made words meaningful, availability of simple models to copy, and cooperative attitudes by the partner that led to instruction or willingness to interpret the learner's tries; (4) the foundation for children's language learning through play is their prior knowledge of the activity structure of the general game type, or in complex games, the specific game; and (5) the language learned in games varies in complexity, with the easiest to learn consisting of syntactically simple, highly repetitive formulae, and with the social success and sense of participation through the language acting as other benefits. (Author/MSE)