This paper will identify specific planning conditions that arise when planning aims at sustainable development. First, attention will be paid tosocio-ethical attitudes toward sustainability issues and to the reasons why much of the sustainability debate deserves an urban focus. Then, specificplanning conditions will be discussed in relation to cities, such as a multiple actor situation, inertia in urban adjustment processes, and asegmentation in planning institutions. Furthermore, the paper will focus on economic behaviour in urban areas using urban sustainability as a broadframe of reference and emphasizing an increasing competition between cities. Then, attention will shift to urban policy in the field of environmentalquality control (urban ecology). A necessary condition for the development of integrated planning for urban sustainability is the development of urbanenvironmental data systems. Attention will therefore, focus on the so-called CBD structue of such information systems (Core - Basic - Distinct data) and the key factors for the success of such systems. The paper proceeds with a discussion of particular data needs in view of Environmental ImpactAssessment. The paper will conclude with the essentials and challenges of an integrated planning approach, major obstacles to such an approach, and aninventoryof directions where some progress already has been achieved.