This paper provides a personal perspective on the recent development of mass spectrometry, arguing that these developments are increasingly driven by the research demands of the life sciences. Within that context, the analytical requirements of proteomics (the determination of the protein constituents of a cell or organism) provide useful examples of the need for very high sensitivity, selectivity to match the required analytical outcomes, rigorous quantification (both relative and absolute) of individual components, and quantitative definition of cellular processes. (c) 2006 Elsevier B.V. All rights reserved.