This paper analyses social change, particularly the processes of social decay, in obsolete and deteriorated housing in the older housing stock in Denmark between 1986 and 1996. These changes are compared with the development which has occurred in similar kinds of housing that have been physically upgraded through a government program for housing renewal. The study shows that this kind of housing attracts a quick turnover of residents and a tendency towards more unemployed or lower income occupants. It is also used by young people as their first home when moving away from their parents. It is also shown that public supported housing renewal stops this type of housing pattern and increases the share of households that have high incomes. The changes, however, are not considerable and there are also many unemployed people among the newcomers. These changes depend to a large degree on the size and tenure of the renewed dwellings. In private renting, particularly co-operatives and in larger dwellings the socio-economic composition of residents undergo greater changes than in smaller dwellings in non-profit or public housing. Extensive renewal often results in high rent compared with rent from the regulated housing market in Denmark. As a result the renewed dwellings have difficulties in competing with other kind of dwellings. For that reason residents of this type of housing primarily consist of welfare or pension recipients or others who receive high housing benefits. A minority of people with higher income also use these dwellings but mostly as temporary housing as after a few years they often move to owner-occupied housing.