The types of knowledge used during requirements acquisition are identified and a tool to aid in this process, ReqColl (Requirements Collector) is introduced. The tool uses conceptual graphs to represent domain concepts and attempts to recognise new concepts through the use of a matching facility. The overall approach to requirements capture is first described and the approach to matching illustrated informally.The detailed procedure for matching conceptual graphs is then given. Finally ReqColl is compared to similar work elsewhere and some future research directions indicated.