The aim of this article is to appraise the new approach to the study of language acquisition by children, which is furthered by the contemporary theory of transformational psycholinguistics (e. g. D. McNeil, 1966; D. I. Slobin, 1968 and others). On the basis of a criticism (supported by some findings of the Soviet theory of speech activity and other researches) of this conception, a new, communicative conception of the study of language acquisition by children is taking shape. Transformational developmental psycholinguistics presupposes that a) language acquisition occurs on the basis of a biologically conditioned inborn capacity for language acquisition, b) this inborn capacity is universal, i. e. common to users of all languages throughout the world, c) the language acquisition by the child is a relatively fast process lasting about 30 months (from the child’s first year of age until the age of 3—4). This theory contains same serious shortcomings, which are discussed in this article. First of all, as regards the so called inborn capacity for language acquisition, it is necessary to point out the following; Man no doubt has certain inborn anatomical and physiological pre requisites for speech activity, but in the actual process of language acquisition by the child the main role is played by the child’s Interaction with other people and the surrounding world, the social conditions under which the child is growing up and the educational environment which influences him. After all, the social basis of language acquisition has already been proved in the basic physiological speech mechanisms (cf. J. Hrbek, 1968). Besides, the language acquisition by the child is not completed at the age of 4—5 years (not even as far as syntax is concerned) as is generally claimed in transformational psycholinguistics, but this process goes on until the age of 9 and beyond (cf. researches by C. Chomsky, and others). This gives rise to the fundamental question: whether a theory based merely on ascertaining linguistic competence provides sufficient perspectives for an adequate study of language acquisition by children. In the author’s opinion language acquisition is a communicative process arid at the foundation of the linguistic behaviour of man there is a more general competence than purely linguistic, namely communicative competence. Communicative competence is essentially the knowledge of social rules of the use of a particular natural language and various non-verbal codes. Linguistic competence is only a part of this more general communicative competence (cf. J. Průcha, 1970 c). In the author’s opinion the study of language acquisition cannot be isolated from all contextual (in the broad sense of the word), socio-cultural and social conditions in which the given process takes place. This conception, by the way, is beginning to be adopted by some other researches as well (T. Slama-Cazacu, 1966; A. A. Leontyev, 1969; M. I. Popova, 1968, and others). This conception involves studying a whole series of problems connected with the communicative behaviour of the child. The main problems of this kind include: 1. Development of the child’s speech depending on the conditions of upbringing and on the socio-cultural factors of the educational environment, 2. the characteristics of the processes of interaction and communication between children and parents, children and other adults than parents, pupils and teachers, and others, 3. ≫the communicative profile≪ of the child with regard to the child’s age, sex, etc., i. e. the intensity and frequency of his communicative contacts with other children and adults in the course of a day and longer periods of time, 4. development of the child’s speech under the influence of mass communication, at school, etc., 5. the content of verbal utterances of the child, and the types of communicative situations which these utterances form a part of, 6. relationships between the types of communicative situations and the formation of the child’s role-taking skill, and the overall socialization of the child, etc. In connection with all these problems the author emphasises the necessity of creating a theory of the development of the communicative behaviour of the child.