Sprawling urban development is one of the major issues that mainly refer to the extent of urbanization. Less urban sprawl and more compact residential development have been viewed as important components of the environmental agenda. In the major cities of developing countries like Istanbul, where the population is over 12 millions, urban sprawl threatens the natural resources through large-scale land consumption. Thus, many policy-makers are starting to look for ways to control sprawl through smart growth policies before it becomes unmanageable. Urban planners require information related to the rate of growth, pattern and extent of sprawl to provide basic measurements for planning strategies. The aim of this research is to provide a sprawl measurement methodology that contributes to the understanding of sprawl dynamics. Using geographic information systems and spatial data, it is possible to identify the pattern of urban sprawl. This paper presents the extent of urban sprawl in Istanbul over six periods from 1975 to 2005.