This paper presents an evaluation of the improvement of air quality due to the use of natural gas in the city of Ankara. A comparison of air quality before and after conversion of a great part of the city to natural gas was made using regional ambient sulfur dioxide (SO(2)) and particulate matter (PM-10 less than 10 mu m diameter) concentrations. Also, there is an overview of construction works that have been carried out, and an explanation of how Geographical Information System (GIS) activities are used to monitor the construction, design and routes of gas pipelines. It is concluded that the long-term project to spread the use of natural gas in Ankara has reduced air pollution to national standards thus improving the quality of life for the city's inhabitants. The changes in the air quality have also brought positive changes in vital fields, such as health, the environment. economy and social life in the city of Ankara, once famous for its seriously polluted air.