This report illustrates the consequences for hazardous waste classification in the Nordic countries by introducing leaching criteria (Criterion H15). Data on secondary aggregates and waste were compared to the proposed H15 criterion and the amounts of waste exceeding the criteria were evaluated. The quality of leaching data and waste statistics varies considerably between countries and waste types. Therefore it is not possible to give a precise estimate of how much waste would have to be classified as hazardous waste if the proposed leaching criteria were introduced. However, the collected data indicated that the amount of contaminated soil, municipal waste incineration bottom ash, fly ash (both coal fly ash and bio fly ash) and metallurgical slag classified as hazardous could be expected to increase substantially if leaching criteria were introduced. The proposed H15 criteria have been developed specifically for protection of groundwater under landfill conditions, based on certain, specified assumptions and scenarios and did not address hazardousness or environmental impacts in general.  The leaching test methods used are not equally suitable for all materials e.g. mining waste, and their applicability depends on a number of prerequisites including sample pre-treatment which can have a significant effect on the results. Such general use of leaching criteria and test methods developed for other purposes could lead to non-harmonised and erroneous classification.