This review describes recently presented instrumental set-ups for aerosol mass spectrometry (AMS), most being suitable for in-situ analysis. AMS allows the analysis of atmospheric aerosol particles within a short time interval and without sample pretreatment, and it is less sensitive to artifact formation than conventional sampling and analytical techniques. Although a quantitative measure of total organic loading can be obtained with some AMS instruments, they currently give only limited information on specific compounds. When the ionization technique produces a large number of fragments for a compound, it becomes impossible to track the original compound. Moreover, at present, there is no commercially available instrument capable of quantitative analysis of chemical compounds in ambient aerosol particles with diameters of 0.003-50 gm and simultaneously offering short time resolution. We pay special attention to the technical and methodological challenges of AMS, whose benefits we demonstrate with selected applications. (C) 2011 Elsevier Ltd. All rights reserved.