This study examines the use of prefabricated language (conventional lexical collocations) in the production of native and non-native writers of English. It first develops a framework for the description of restricted collocations and then reviews experimental research into the psycholinguistic processing of prefabricated language. Computer-based corpora of native and advanced non-native academic writing are analysed to discover to what extent and how such collocations are used in formal written English. Pedagogical implications are then considered, and the final part of the study examines the selection and presentation of restricted collocations in general and phraseological dictionaries for learners. The conclusion suggests that advanced learners need specialist collocational dictionaries, and the results of this research help to establish principles for the design of such dictionaries.