This paper discusses the issue of residential segregation in Halmstad, a municipality in western Sweden. The inhabitants themselves say that it is one of the most segregated municipalities in the country and the growing segregation is affecting the community in various ways, particularly in the housing market, where increased segregation has resulted in decreased quality and safety in these areas, as well as decreased cohesion between different areas in the municipality. The paper aims to explain the forms of residential segregation in society using four theories: The planning hypothesis, market hypothesis, status hypothesis, and contact hypothesis. The research method used is the case study method, which is suitable for analyzing a “case” of broader phenomenon. One method that has been considered appropriate within the case study literature for testing theories, as this study does, is pattern matching, also known as congruence matching. This method tests the extent of which the empirical pattern matches the hypothetical pattern that the theory assumes. If there is lack of congruence between the empirical pattern and the theoretically assumed pattern, the result speak against the theoretical hypothesis. If the congruence is found, the theoretical hypothesis is supported. The planning hypothesis could confirm that the municipality ́s planning has had segregated effects and the efforts have not been sufficient to counteract residential segregation. The market hypothesis could not be confirmed because the housing market is not governed by market rents. The paper also found patterns that strengthened the status hypothesis. Partly by finding material that shows that Halmstad is a polarized municipality with areas that have lower status than others. Lastly, the contact hypothesis could partly be confirmed by looking at increased family immigration.