Students and other debutants have difficulty in orientating themselves in the BPI. Personalized assistance being impossible, the library has decided to facilitate their access by pointing out, by means of a coloured badge, easiest books. After a first experiment which was, in 1987, limited to books of biology, botany and zoology, this signalling has been extended to the whole library in April 1989. It is directed to adolescents and unexperienced adults, but also to amateurs and occasional visitors in search of a basic book about a current topic or a matter of leisure. The books chosen have to be clear and easily understandable ; they should not require a specialized vocabulary nor a previous knowledge of the subject-matter. At the present time, 8500 items constitute 3 % of the whole stock.