Particulate matter (PM10) is one of the air pollutants, which pose a major risk to public health. This is why EU legislation has set limit values for PM10. In case of persistent and high exceedances of these limit values the “Directive 2008/50/EC on ambient air quality and cleaner air for Europe” proposes air quality plans as a complex, though effective, instrument to reduce air quality level exceedances. Developing and appropriately applying air quality plans requires particular expertise at the levels of affected municipal authorities, of data collecting authorities, of modelling engineering offices and of supervising regional authorities. The “Guideline on Air Quality Plans” has been developed during an advisory assistance project with Bulgaria. It presents the most important aspects, which have to be taken into account when developing and revising air quality plans. Complex topics are illustrated by easily understandable figures. References to the Bulgarian case provide the link between theory and practice. A comprehensive selection of potentially appropriate mitigation measures is listed at the end of the document.