From the 1st to the 6th of September 2013 in Langen (D), 7 Laboratories of WHO/AQUILA (Network of European Air Quality Reference Laboratories) met at a laboratory comparison exercise to evaluate their proficiency in the analysis of inorganic gaseous pollutants covered by European Directive about air quality (SO2, CO, NO, NO2 and O3). The proficiency evaluation, where each participant?s bias was compared to two criteria, provides information on the current situation and capabilities to the European Commission and can be used by participants in their quality control system. On the basis of criteria imposed by the European Commission, 75.7% of the results reported by the laboratories were good both in terms of measured values and reported uncertainties. Another 20.9% of the results had good measured values, but the reported uncertainties were too high and for 2.0% values the uncertainty was underestimated. 1.4% values were questionable. Comparability of results among participants at the highest concentration level, excluding outliers, is acceptable for NO, SO2 and O3 measurements while NO2 and CO one showed less satisfactory results.