Studies of bilingual infants are in disagreement as to the point at which the child distinguishes two languages in his linguistic environment. In this paper, data from two classic works by linguist-parents on bilingual infants are compared with data collected from the author's own bilingual daughter. Five types of behavior are described which might provide evidence that the child is able to perceive the existence of two language systems earlier than has been proposed. In discussion of the possession of two "native" languages by the bilingual child, data from the author's daughter is presented, showing her to possess two coexisting grammars and social norms for the use of each. This data was collected by videotape when the child was 3 years old. This study is relevant to questions of the metalinguistic abilities of bilingual children and to educational programs which receive and educate the truly bilingual preschooler. (Author)