Each year Member States have to report to the European Commission on the exceedances of air quality limit values which occurred on their territory. Quantitative information is required about the areas and population exposed to such exceedances. A probabilistic methodology for defining exceedance zones has been developed, based on preliminary air quality mapping. Atmospheric concentration fields estimated by kriging and the corresponding kriging variance are used to identify areas where the exceedance or non-exceedance can be considered as certain and areas where the situation with respect to the limit value is indeterminate. The methodology is applied on national and urban scales focusing on exceedances of PM10 daily limit value and NO2 annual limit value. Results are discussed from operational perspectives.