Apparently, breathing clean air is of significant importance to human beings and thus attention to what enters our body through inhalation is on the increase. Tehran’s air pollution has received considerable media coverage in recent years: Since particulate matter (TSP and PM10) is one of the important pollutants in this city, an attempt was made to study TSP and PM10 concentrations and to make a qualitative assessment of air using the Air Quality Index (AQI), with TSP and PM10 sampling both daily and on a monthly basis. Shariati Hospital district was selected as study area from 22 December 2001 to 20 April 2002. To determine the amount of TSP and PM10 according to EPA and WHO standards, 61 samples were taken for TSP and 61 samples for PM10 with High Volume Sampler. The results indicated that: • As for TSP and PM10, the period extending from 20 February to 20 March (Esfand) was the most heavily polluted one in this study. The cleanest spell was observed from 21 March to 20 April (Farvardin). • Saturdays and Mondays were the most polluted days of the week for TSP and PM10 and Fridays were the cleanest. • As for TSP, In 51 percent of the samples the Air Quality Index (AQI) was below 100 (AQI<100) and in the remaining 49 percent, AQI was above 100 (AQI>100). • In the case of PM10, in 75.5 percent of samples the Air Quality Index (AQI) was below 100 (AQI<100) and in the remaining 24.5 percent AQI was above 100 (AQI>100).