This speech, presented at the 1977 meeting of the World Organization of Preschool Education (OMEP), proposes that the preschool linguistic environment determines language facility, which affects later school and work success. The normal course of communicative ability is traced. It is proposed that although most children, in and out of preschool, learn to speak effortlessly and naturally, the preschool is able to favorably affect the type of linguistic environment and therefore the child's facility with the language. Research on children's use of language is examined, specifically, the child's role in language development. Findings are discussed in terms of language learning programs. (SB)