This report - linked to the technical documents of the OECD manuals for the measurement of R&D activities ("Frascati Family") - presents the essential elements of bibliometrics and its application to the analysis of research systems. Bibliometrics is based on the enumeration and statistical analysis of scientific output in the form of articles, publications, citations, patents and other, more complex indicators. It is an important tool in evaluating research activities, laboratories and scientists, as well as the scientific specialisations and performance of countries. The report, having set the background for the development of bibliometrics, presents the databases on which bibliometrics is built, as well as the principal indicators used. Twenty-five examples are presented at the end of the document, illustrating the various uses of bibliometric methods for analysing research systems. These indicators measure scientific output, by counting the number of papers; the impact of ...