In the present study, a new METADISCOURSE typology is presented with ten subtypes: connectives, topicalizers, reminders, intention markers, interpretive markers, hedges, emphatics, attributors, persona markers, and relational markers. The first five constitute textual METADISCOURSE, and the rest constitute interpersonal METADISCOURSE. This study also investigates the impact of language/culture on the use lf METADISCOURSE in the Masters theses of 3groups: native (Iranian) speakers of persian non-native (Iranian) speakers of English, and native (British) speakers of English. The introductions and discussions of these theses were compared for amounts and types of METADISCOURSE used, by means of a number of split ANOVAs. The different groups were found to use METADISCOURSE types differently; more specifically, they were found to use connectives, hedges, attributors, and persona markers differently from one another. This study has implications for a number of disciplines, in particular teaching English as a foreign language.