Abstract. The term bilingualism here suggests the acquisition of two languages during the first six years of life. This definition includes the following conditions: (a) Children are able to comprehend and/or produce linguistic aspects of two languages. (b) Children are exposed "naturally" to the two systems of languages as they are used in the form of social interaction during early childhood. This condition requires a substantive bilingual environment. In many cases this exposure comes from within a nuclear and extended family network but this need not be the case (visitors, and extended visits to foreign countries are examples of alternative environments). (c) The simultaneous character of development must be apparent in both languages. This is contrasted with the case of a native speaker of one language, who after mastery of that language, begins on a course of second language acquisition. It is the preceding combined conditions which define the present population of interest. It is clear from this definition that an attempt is made to include the child's linguistic abilities in conjunction with the social environment during an important "developmental segment" of life and at the time of learning second language.