The present study is designed to establish how lexical context influences the MMN latency and amplitude when the pseudowords are presented. The ERPs were recorded by using only pseudowords or а pseudoword and words with different lexical frequencies. We found the generation of different MMN patterns when the same pseudoword was presented in different contexts. The pseudoword presented in context with another pseudowords demonstrated the smaller amplitude and the bigger MMN latency. Whereas the same pseudoword presented in context with words led to the significantly enhanced amplitude and the decreased latency of MMN. It is supposed that the pseudoword presented in context with words is perceived as conceptually different stimulus leading to the significantly enhanced MMN. Moreover, the hypothesis of lexical frequency influence on MMN has been supported. We found that the presentation of a high-frequency word led to the significantly more pronounced MMN response relative to a low-frequency one [1; 2, p. 717; 3