Engineering design, despite its technical mechanical and mathematical foundations, is heavily informational. Many authors have used information as the focus of their research; in contrast, our study examined both information needs and document usage by engineers. After reviewing the design decisions behind the diary study; we report on the analysis of the data. We also used the data to generate new ‘document use’ scenarios, and ‘proof of concept’ test of a related software system. As with all research methods, diary studies have a number of strengths and weaknesses so we also provide some reflections on the use of diary studies as a method for examining the engineer's use of documents in the engineering domain.