The changing nature of chemical information literacy over 50 years is examined by a comparison of a number of guides to chemical literature and information. It is concluded that: an understanding of the world of information is the sole aspect to have remained important and essentially unchanged over time; that knowledge of sources, ability to access information and ability to organize information have been of importance throughout, but have changed their nature dramatically; and that evaluation of information has gained in importance since the advent of the World Wide Web. The link between chemical structure and corresponding substance information is the most significant threshold concept. Information literacy in chemistry is strongly subject-specific.