This publication collates the proceedings of the Workshop on Demonstration of Equivalence between Ambient Air Monitoring Methods, which was held at the JRC in Ispra (VA) from 2 - 4 May 2007 and the major discussions vis-à-vis the last version of the "Guideline on demonstration of Equivalence". The extensive use by national reference laboratories of this guideline strengthens the principles on which the current guideline is based.