This article presents an overview of measuring science based on a bibliometric methodology. The 2 main lines of this methodology are discussed. First, the measurement of research performance is addressed, including aspects such as interdisciplinarity, collaboration, and knowledge users. It is demonstrated that advanced bibliometric methods are an indispensable element next to peer review in research evaluation procedures, particularly at the level of research groups, university departments, and institutes. Problems involved in the application of bibliometric analysis in the social sciences are discussed. Next, an introduction to the mapping of science is presented, focusing on basic concepts and issues of practical application of science maps. These maps are unique instruments to discover patterns in the structure of scientific fields, to identify processes of knowledge dissemination, and to visualize the dynamics of scientific developments. Their potential for unraveling interdisciplinary developments and interfaces between science and technology is discussed. The article concludes with an indication of the limitations and possible problems of bibliometric analysis. (Contains 3 figures, 1 table and 5 footnotes.)