The purpose of this Wiki is to pool experiences gained by dispersion modellers during their work. Warnings against pitfalls and common mistakes are of high interest. Researchers are encouraged to report on pitfalls that they encounter, and which they would like to warn others against. The Wiki was founded in November 2005, following the 10th conference on Harmonisation within Atmospheric Dispersion for Regulatory purposes where the idea of a Wiki was launched. The web page http://www.harmo.org/Conferences/Crete/Wiki_Introduction.asp introduces the ideas behind the Wiki.