Atmospheric aerosols have recently attracted considerable attention due to their effects on climate, atmospheric chemistry, and health. This interest has triggered a variety of activities including the development of new analytical methods for a better characterization of atmospheric aerosol particles, some of which are presented here. Emphasis is laid on the description of methods for on-line and in situ analysis, since the analysis of many processes requires a good time resolution, and since in situ analysis methods are less prone to sampling artefacts.