Das Projekt "COST 710 - Harmonisierung des Pre-Processings meteorologischer Daten fuer atmosphaerische Ausbreitungsmodelle - Arbeitsgruppe 2 Mischungshoehenbestimmung" wird vom Umweltbundesamt gefördert und von Universität für Bodenkultur Wien, Institut für Meteorologie und Physik durchgeführt. This was an activity within COST Action 710 which is concerned with the harmonisation of meteorological preprocessors for operational dispersion models. Working group 2, chaired by Petra Seibert, compiled methods and modules for the determination of mixing heights, reviewed and compared them on the basis of several data sets. Recommendations for users as well as developers of such modules were worked out and needs for further research were identified.