||The aim of this paper is to test an indicator that can represent the process of decline of a specific type of urban area: the industrial estate. We use data on decline derived from fieldwork on industrial estates in the Netherlands to test whether the development of property values on these industrial estates is a reliable indicator to measure decline. The identification of a reliable indicator enables the systematic analysis of processes of decline of industrial estates, which has received little attention in the vast body of literature on urban decline. This paper comprises two parts. In the first part, a connection between urban decline literature with literature on the valuation of individual property is made. Urban decline at the level of individual urban areas, often referred to as neighbourhood decline or decay (Cheshire and Hay 1989) is much researched in urban literature. However, apart from inner city commercial areas, mostly residential neighbourhoods have been the topic of research in studies of urban area decline (see e.g. Broadway and Jesty (1998) and Medhurst and Lewis (1969)). Other parts of the city appear to be mostly neglected. Rather than adding to the already extensive literature on urban decline, the state of art on this literature is presented. Literature on the valuation of property is added to identify an indicator for decline of industrial estates. The second, empirical part of this paper, focuses on fieldwork that was conducted in the Netherlands. A study of the present quality of more than 600 industrial estates in the South of the Netherlands will be compared to the development of property values on the same industrial estates. By bringing this together the hypothesis whether the development of average property values could serve as an indicator for decline of industrial estates, is tested. A proper indicator for decline of industrial estates is expected to be useful in at least two ways. First, this indicator will enable further analysis, seeking to explain why the decline of industrial estates (or other urban areas) takes place. Second, the majority of governmental redevelopment schemes (in the Netherlands and elsewhere) are aimed at the level of the urban area. More knowledge on the actual causes of urban area decline will help the responsible government organisations to better target revitalisation subsidies to obsolete urban areas in general and industrial estates in specific. This paper is organised as follows. In section 2, obsolescence of urban areas will be defined and by studying property valuation literature, the factors that cause decline of industrial estates will be presented. This will lead to the conclusion that development of the average property value in a certain urban area can be an indicator for decline of that area. In section 3 the empirical work will be presented. The present quality of the sample of industrial estates will be compared to the development of average property value. Section 4 draws the main conclusions and discusses their implications.