Gentrification is a process describing the revitalisation of urban districts by which the local population is displaced by households of higher incomes. Particularly over the last years, there are controversial debates about gentrification, some arguing that gentrification results in social separation and others promoting it as a way to establish social mixing. Focussing on the case study of Hamburg-St. Pauli, this thesis aims to analyse the causes and consequences of gentrification towards the development of an urban district, particularly concerning changes in the residential and socio-demographic structure. As a basis for the detailed analysis of the case study I had a closer look on the theoretical background of gentrification, regarding different definitions and theoretical approaches as well as consequences. Following, the case study analysis is divided in two parts. First, in order to describe the development of Hamburg-St. Pauli, I had a closer look at its history and at its present situation. Therefore, I made use of books and newspaper articles, and I conducted interviews with persons involved. Second, I examined official data and statistics of different years giving information about changes in the population structure, social structure and residential structure of Hamburg-St. Pauli. Comparing those numbers to data relating to the county of Hamburg-Mitte and the city of Hamburg it was possible to evaluate on-going transformation processes in an overall context. Further, due to a conducted residents‘ survey, it was possible to define different perceptions and evaluations concerning the effects of the gentrification process. Concluding, the process of gentrification in Hamburg-St. Pauli cannot be explained on grounds of one but on several circumstances. Statements of local residents as well as of interviewees showed both positive and negative evaluations of the process, and therefore former assumptions and theoretical approaches concerning the controversial consequences and the contradictory character of the process can be supported.