The design process in component-based software engineering needs to implicitly incorporate ways of reusing existing components. Reuse in turn implies the need to acquire knowledge about any components that might be incorporated into a system. Our paper describes an empirical study of how component documentation can be used to help develop that knowledge, using Unix processes as the source of documentation and components, and using both think-aloud and non-intrusive techniques to record subject behaviour. Our conclusions suggest how component documentation might be organised so as to assist with reuse, and identify further questions about its form.