1st proofs A corpus-based comparison of syntactic complexity in NNS and NS university students’ writing Haiyang Ai and Xiaofei Lu his paper reports on a corpus-based comparison of syntactic complexity in NNS and NS university students’ writing. We analysed 600 essays from the Written English Corpus of Chinese Learners and the Louvain Corpus of Native English Essays using 10 syntactic complexity measures to investigate whether and the extent to which NNS and NS university students’ writing difers with respect to length of production unit, amount of subordination, amount of coordination, and degree of phrasal sophistication. Results showed signiicant diferences in all four dimensions of syntactic complexity between the writing of NNS students at both low and high proiciency levels and that of NS students. his gap calls for the design of pedagogical interventions to enhance NNS university students’ syntactic development. 1. Introduction Syntactic complexity, i.e. the range and degree of sophistication of syntactic struc- tures that surface in language production, has been recognized as a very important construct in second language writing teaching and research (e.g. Ortega 2003). A large variety of syntactic complexity measures have been proposed in the second language writing development literature, and numerous second language writing development studies have been conducted to determine which of them constitute valid and reliable developmental indices that can be used by second language teachers and researchers to objectively gauge second language learners’ develop- mental level or global proiciency in the target language (e.g. Larsen-Freeman 1978, 2009; Wolfe-Quintero et al. 1998; Ortega 2003; Lu 2011). Whereas researchers have approached second language writing proiciency with diferent conceptualizations, a native-speaker (NS) baseline appears to be a rather neglected dimension in the examination and assessment of the performance and developmental level of non-native speakers (NNS) in the target language