The thesis researches the reasons of shrinking cities, especially the impact of deindustrialisation, in Germany using the example of Halle and Gelsenkirchen. Additionally, the policy response towards this phenomenon in terms of urban consolidation in the cities is posed. For doing that, the economic history of the towns is investigated and simultaneously the development of population and of unemployment is researched, as they are closely connected to the economy. With an analysis of the proportion of employees in the different economic sectors in the course of time the structural change becomes more obvious. A shifting has taken place: both cities engage currently more people in the tertiary sector and less people in the secondary sector as twenty years ago. Concluding all indicators it can be said that a deindustrialisation took place. However, also other influences on shrinking, as for example migration, are described and their impact on both cities is explained. With investigating the consolidation areas of the programme Stadtumbau Ost and Stadtumbau West in Halle and Gelsenkirchen the possible course of action by the policy is presented and those areas in Halle and Gelsenkirchen are identified, which have the biggest population decline and the highest vacancy rates. Critique about the Stadtumbau programme is given at the end of the research. The result of the analysis is that deindustrialisation can explain big parts of the shrinking process in both cities. Thought, it has to be taken into consideration that the collapse of the German Democratic Republic has been speeding up the process of deindustrialisation in Halle and also other influences like migration and the demographic change affect the growth or shrinking of cities. The urban consolidation in the cities is a mean to alleviate the urgent consequences of shrinking and to retrieve especially the big housing societies from insolvency. However, the applied modification measures cannot alter the causes of shrinkage.