The information services of public libraries, with their wide readership, have to face directly the challenge of our rapidly changing society. Nowadays, due to the impact of information technology, public libraries await a transformation. In this article, the new challenges which public libraries are now facing are analyzed via the transition of time, the changing characteristics of readers and the multiplicity of access channels to informations. We describe the new appearance of public libraries in the network age in terms of their new roles, new services, new resources and new systems.