The important yet under-researched role of item writers in the selection and adaptation of texts for high-stakes reading tests is investigated through a case study involving a group of trained item writers working on the International English Language Testing System (IELTS). In the first phase of the study, participants were invited to reflect in writing, and then audio-recorded in a semantic-differential-based joint discussion, on the processes they employed to generate test material. The group were next observed at a simulated item writers' editing meeting to refine their texts and items for an IELTS reading test module. The participants' written descriptions and recorded discussions provided rich data on how source texts were perceived, selected and adapted for the Test. The study reports findings from textual analyses using indices of readability and lexical density from the original material sourced by the item writers and their adapted versions for the test. Results from qualitative and quantitive analyses are discussed in terms of the implications for the IELTS reading module of editing actions such as: reducing redundancy and technical language, changing styles, deciding on potentially sensitive issues and relationships between texts and test items. The important issue of text authenticity in tests such as IELTS is also broached. (Contains 4 tables and 2 figures.)