This paper adopts an automated frequency-driven approach to identify frequently-used word combinations (i.e., "lexical bundles") in academic writing. Lexical bundles retrieved from one corpus of published academic texts and two corpora of student academic writing (one L1, the other L2), were investigated both quantitatively and qualitatively. Published academic writing was found to exhibit the widest range of lexical bundles whereas L2 student writing showed the smallest range. Furthermore, some high-frequency expressions in published texts, such as "in the context of", were underused in both student corpora, while the L2 student writers overused certain expressions (e.g., "all over the world") which native academics rarely used. The findings drawn from structural and functional analyses of lexical bundles also have some pedagogical implications. (Contains 12 tables, 2 figures and 5 notes.)