Abstract
Citation analysis provides a tool for the evaluation of the relative importance of journals as well as papers. A publication, the ISI Journal Citation Reports, is issued primarily to permit users to make such evaluations by answering the basic questions: How often has a journal been cited? What journals have cited it and how frequently? What journals has it cited and how frequently? These data have been conditioned by the inclusion of a `relative impact factor' to give additional weight to the significance of the articles it publishes. The information thus developed is particularly attractive to librarians, journal editors and publishers, individual scientists, and science policy-makers.