Planners and politicians are searching for action plans to increase the environmental quality and sustainability in the large cities. But the search is hampered by the lack of theory. The confusion over the issues of quality and sustainability stems from the fact that theories are formulated on a general and abstract level. What is needed is a theoretical framework to analyse the empirical observations on the existing urban environments. We need a systematic descriptive classification of the urban structure on the microlevel. The paper outlines a methodology of classification of Swedish urban types. The classification is based on parameters that can be obtained from central data bases. The registration of objects will be implemented in a Geographical Informations System (GIS). The result is (a) reliable descriptions (maps, data bases) of the existing urban structure in a given city and, (b) in the long term, new knowledge of the relationship between urban form and environmental capacity.