The purpose of this fastback is to help teachers find out how children acquire a second language and explore the linguistic foundations on which sound English as a Second Language (ESL) curricula can be developed. It is intended for the regular classroom teacher, not the ESL specialist. Central findings in research on second language learning include these: that there is an order in which language structures are acquired; this order differs from the traditional grammar sequence taught; fluency develops gradually and subconsciously; and formal learning of grammatical structures follows. Three conditions are necessary for second language learning: perception of a need to communicate in the target language; comprehensible input; and a low-anxiety environment. Children go through four stages in second language learning: pre-production; early production; speech emergence; and intermediate fluency. They proceed through these stages at their own pace, and forcing can delay progress. The teacher's role is to structure an environment in which the learner finds it necessary to communicate, using a variety of techniques so the message transmitted is understood. Above all, the teacher should take an interest in the child's first language and culture, and should accept all attempts made to communicate. Caretakers should provide an environment rich in language experiences and cooperate with the school in second language teaching efforts. Teachers must understand that the child learned his native language easily, and can learn the second similarly. Teacher knowledge of the native language is not required for effectiveness. (MSE)