This study provides a critical overview of the recently developed theory of Hittite-Luwian bilingualism mostly by H. Cr. Melehert, E. Rieken and Th. Van den Hout. After a short presentation of the linguistic map of Late Bronz Age Anatolia and the problem whether Hittite was a spoken language until the end of the Empire a detailed discussion of linguistic arguments of Luwian influence on Hittite grammar will follow. The third part of the study focuses on the possible historical and demographic reasons hidden behind this bilingualism.