The history of ancient libraries has traditionally be written around major bibliographic projects such as the Library of Alexandria and the imperial libraries of Rome, projects that are the subject of most ancient testimonia. Recent research - papyrological, epigraphic and archaeological - has raised some doubts about the scale of those projects and also emphasized the key role played in textual transmission by the collections of private individuals and small textual communities. Drawing on this work I shall suggest a new approach to the history of ancient libraries.