A Continuous Air Quality Monitoring Station (CAMS) has been established in Dhaka city, at the campus of the Parliament House (Sangsad Bhaban), and is operational since April 2002. Six criteria pollutants namely, PM10 and PM2.5 NOx, S02, O3 and CO have been monitoring in the CAMS. As particulate matter is the most responsible air pollutant in Dhaka City, results on trend analysis of PM including their seasonal variation are discussed in this paper. On the basis of these observed results and their validation by comparison, daily air quality index (AQI) for Dhaka city has been calculated following the US EPA model. The results so far obtained indicate that Dhaka air quality is good for about 7 months of the year, April to October (monsoon period). Deterioration in this index starts from November and it continues up to March of each year (non monsoon period). Temporal variation of the levels of air particulate matter (PM2.2-10, PM2.2 and BC) was studied at two air particulate matter (PM) monitoring stations in Dhaka. One site is a semi-urban area in Dhaka, located within the Atomic Energy Centre, (AECD), with relatively less traffic. The other site is a hot spot area with very high pollutant concentrations because of the proximity of major roadways. The samples were collected using a 'Gent' stacked filter unit in two fractions of 0-2.2 ìm (fine fraction) and 2.2-10 ìm (coarse fraction) sizes. It has been found that the fine particulate matter in Dhaka has decreasing trend from the previous years due to various Government policy interventions. Positive matrix factorization (PMF) technique was utilized to apportion the possible sources of atmospheric aerosols in these areas. The possible sources are motor vehicle, soil dust, road dust, emissions from construction activities, sea salt, biomass burning/brick kiln, re-suspended/ fugitive Pb, and two-stroke engine. A large fraction (about 50%) of the PM2.2-10 mass at both sites comes from soil dust and road dust. The motor vehicle including two strokes contributes about 48% of the PM2.2 mass of both areas in Dhaka. PMF modeling could resolve about 3% of the total PM2.2 mass as re-suspended / fugitive Pb. Although, unleaded gasoline has been introduced in Bangladesh since July 1999, some Pb still left in PM.