This book explores the application of an innovative assessment approach known as Dynamic Assessment (DA) to academic writing assessment, as developed within the Vygotskian sociocultural theory of learning. DA blends instruction with assessment by targeting and further developing students’ Zone of Proximal Development (ZPD). The book presents the application of DA to assessing academic writing by developing a set of DA procedures for academic writing teachers. It further demonstrates the application of Hallidayan Systemic Functional Linguistics (SFL), combined with DA, to track undergraduate business management students’ academic writing and conceptual development in distance education. This work extends previous DA studies in three key ways: i) it explicitly focuses on the construction of a macrogenre (whole text) as opposed to investigations of decontextualized language fragments, ii) it offers the first in-depth application of the powerful SFL tool to analyse students’ academic writing to track their academic writing trajectory in DA research, and iii) it identifies a range of mediational strategies and consequently expands Poehner’s (2005) framework of mediation typologies. Dynamic Assessment of Students’ Academic Writing will be of great value to academic writing researchers and teachers, language assessment researchers and postgraduate students interested in academic writing, alternative assessment and formative feedback in higher education.