This paper will present a theoretical analysis of research on metalinguistic understanding, illustrating how current research does not yet adequately address metalinguistic development in writing. Existing research on metalinguistic understanding has focused more on language acquisition, oral development and bilingual learners. Research on metalinguistic understanding in writing has tended to look more closely at young learners developing writing skills in spelling, transcription and orthography. Thus, theoretical accounts of metalinguistic understanding are currently insufficient to explain developing metalinguistic mastery of composing text and the relationships between declarative and procedural metalinguistic knowledge in writing. If we are to understand better the nature of metalinguistic understanding in relation to writing in learners in the later phases of compulsory education, it is important to develop theoretical clarity about the key concepts involved in order to frame empirical studies which are both conceptually and methodologically rigorous and educationally relevant.