Particulate matter pollution is one of the major environmental concerns in Pakistan. Over the past 20 years there has been a considerable increase in the number of motor vehicles. The present study was conducted to assess journey time and roadside exposure to particulate matter and carbon monoxide along major roads of Lahore during November, 2007. Measurements of particulate mass and carbon monoxide were carried out continuously inside an air conditioned vehicle, while commuting, and outside the vehicle at 36 different locations in the city. Additionally, monitoring was undertaken at a background site throughout the period. The overall mean journey-time concentrations of PM10, PM2.5, PM1, PM10–2.5 and CO were 103 μg/m3, 50 μg/m3, 38 μg/m3, 53 μg/m3 and 8 ppm, respectively. At the roadside average PM10, PM2.5, PM1, PM10–2.5 and CO concentrations were 489 μg/m3, 91 μg/m3, 52 μg/m3, 397 μg/m3 and 4 ppm, respectively. The highest levels were found at the sites with traffic congestion reflecting, not only, the large contribution of automobile exhaust but also the resuspension of road dust. The majority of public transport vehicles in Lahore are not air-conditioned and it is very likely that commuters are exposed to the similar high levels of pollution.