This workwill focus on the urban expansion around the National Park of Tijuca, an area of environmental protection within the city of Rio de Janeiro, anurban center with a population of approximately 6.300.000 inhabitants and 1023 registered slums. The main objective is to study, through estimates made using satellite images and aerial photos, the modification in the land use in eight slums situated around the park (Borel, Cerro Corá, Complexo do Turano, Mata Machado, Vila Parque da Cidade, Rocinha, Salgueiro e Santa Marta) during a ten year period from 1999 to 2009. Two specific aspects, concerning new constructions above 100m of altitude and on slopes with declivity superior to 45 degrees, will be examined in detail, since they are restrictions provided by law. With the use of geographic information systems and visual interpretation of images, several important conclusions were obtained about the expansion tendency of these slums. In all of them the growing rate was at least 3.6 per cent above the 100m altitudeand at least 1.6 per cent in areas with declivity superior to 45degrees, indicating that these populations are exposed to serious risks of landslides. On the other hand, it was also possible to notice the good results of the reforestation policy, initiated by the City of Rio de Janeiro in 1987, given the positive variations in the areas of vegetation observed in several of the slums analyzed in this work.