The present study examines the variation of ambient aerosol (PM10) concentrations in Karachi, city. Samples were collected from ten different locations, representative of urban background, residential, traffic and industrial areas from 2007 to 2011. At each location, PM10 was measured continuously from 08:00 am to 06:00 pm at local time. The maximum 10 h average particulate matter (PM10) mass concentrations were found at Tibet Centre (440.1mg/m3) and minimum at PCSIR Campus (21.7mg/m3) during 2008. A rising trend during 2008 may be due to the civil works for bridges and extension of roads at different locations in Karachi. The results also suggest that urban traffic and industrial areas appeared to have higher PM10 concentration than residential and background areas.