The impact factor of scientific reviews, calculated by the Institute for Scientific Information (ISI), is increasingly used to evaluate the performance of scientists and programmes. Bibliometric indicators, originally designed for other purposes than individual evaluation, are very useful tools provided their interpretation is not extrapolated beyond their limits of validity. Here we present a critical analysis of appropriate uses and misuses of bibliometric data based on case studies. We also outline anticipated consequences of new information technologies, such as electronic journals or open access schemes, on the mode of science production, evaluation and dissemination in biomedical sciences.