Background & methodology · The purpose of this report is to review existing data on hazardous waste for the period 1993-1996 and to try to improve the comparability of the data. The report has been prepared by the European Topic Centre on Waste (ETC/W) as part of the work programme of the European Environment Agency (EEA). · Austria, Denmark and Ireland are included in the comparability study as well as one region in Germany (North Rhine-Westphalia) and two regions in Spain (the Basque Country and Catalonia). These countries and regions produce all together 6.5 million tonnes hazardous waste per year. This is approximately 1/5 of the total hazardous waste generation in all EEA member countries. · When comparing the generation of hazardous waste across countries, it is very important that the reported figures are based on the same definitions, i.e. that a common classification is applied. However, in the case of Austria, Denmark, Germany, Ireland and Spain different classification systems were applied when the data originally were registered. · In order to make a comparability possible a common classification has been applied. The common classification used is the Hazardous Waste List. which is a part of the European Waste Catalogue. Key findings · Even though it is difficult, the study has proved that it is possible to reclassify most of the hazardous waste, which was originally registered according to a national or regional classification system, according to the Hazardous Waste List and the European Waste Catalogue. Thereby, it has been possible to establish data sets for hazardous waste, which can be compared. · The variations in hazardous waste generation between Austria, Denmark, Ireland, Germany (North Rhine-Westphalia) and Spain (the Basque Country and Catalonia) can first of all be explained by the fact that, even though the Hazardous Waste List and the European Waste Catalogue have been introduced, they do not sufficiently describe what is regarded and reported as hazardous waste in each country or region. The amounts of hazardous waste that may be related directly to the Hazardous Waste List varies between 27 % and 71 %. · If the Hazardous Waste List is amended as proposed by the Commission, the amount of hazardous waste that may be related directly to the Hazardous Waste List will increase to 55-80 % for examined countries and regions. This means that the degree of comparability of hazardous waste generation between countries and regions would increase. · Different types of hazardous waste dominate in the examined countries and regions. · In each of the examined countries and regions a relatively small number of waste types represent a large proportion of the total hazardous waste generation. On average, the 20 largest generated waste types represent approximately 75 % of the total waste generation. · In general, the industrial structure is an important factor in explaining the variations of hazardous waste quantities in the different countries and regions. Significant differences exist within the respective manufacturing industries, energy production sectors and waste incineration activities. · It has proven difficult to relate hazardous waste classified according to national or regional substance orientated classifications to the Hazardous Waste List and the European Waste Catalogue. Therefore, when the work of comparison is extended to all other EEA member countries, it is recommended to ask for information only on the 20 largest generated waste types in each country.