Because of residential heating in winter months air quality may be negatively affected in big cities. In this study, the annual and seasonal distribution of sulfur dioxide (SO2) and particulate matter (PM) concentrations, measured between 1988 and 2003 in seven districts of Bursa, have been studied. Average concentration values were determined based on measurements taken from these 7 districts and these values fluctuated between 90,2 +/- 59,1 mu g/m3 and 23,5 +/- 20,8 mu g/m(3) for PM, 218,4 +/- 159,3 mu g/m(3) and 44,8 +/- 39,9 mu g/m(3) for SO2. Improvements in air quality after 1992, when natural gas usage was started, was discussed. Measurements of PM and SO2 taken from Bursa were compared with the limits in Turkish Air Quality Control Regulation (TAQCR) and measurements from different locations.