The paper has two goals: one is to examine Vygotsky`s linguistic psychology from his whole theoretical framework, the other is to construct a new linguistic horizon from this examination. I think one of the most important theoretical contributions he made is the concept of sign-mediation, especially that of language-mediation in the growth process of mind which is well developed and demonstrated by main research themes in his Thought and Language(1934). Theoretical results of his experimental research on such a concept argue that linguistic competence is not determinated only by its innate structure but also by its complex developmental process synthesized with higher mental functions like thought, memory, imagination. By this is proved clearly that the contemporary cognitive theory based on the hypothetical concept of universal - innately determinated, thus static - linguistic competence and its language acquisition model must be necessarily modified by accepting such a developmental, dynamic concept. Vygotsky`s another interesting linguistic contribution is the distinction between meaning (значение) and sense (смысл) of the word; the former is relatively invariant, whereas the latter presents variable, dynamic character and permanent tendency toward a kind of open polysemy. But in so far as the predominance of sense over meaning is an undeniable empirical fact on the level of utterance, a realistic linguistic semantics must take it into a serious consideration theoretically.