This paper explores the degree of variability in the structure of research article introductions within a single discipline. It is an exploratory study based on the analysis of 20 research articles. The study investigates the differences between two subdisciplines of applied linguistics, namely second language acquisition and second language writing research, in terms of Swales's [Swales, J. M. (1990). Genre analysis: English in academic and research settings, Cambridge: Cambridge University Press] CARS model. Some subdisciplinary variation was identified. The two subdisciplines seemed to employ different and almost unrelated move structures. In the second language acquisition corpus one type of move structure was predominant while in the second language writing corpus two different types of move structure were almost equally frequent. It is suggested that these differences can be explained in terms of the concepts of "established" field and "emerging" field. (c) 2005 The American University. Published by Elsevier Ltd. All rights reserved.