The hot emissions of CO, NOx, SO2, TSP, and VOCs were estimated for the traffic in Medellin city (Colombia). The VOC emissions was grouped into 5 categories: metane, alkanes, alkenes, aromatics and aldehydes. The total study area was 360 km2, involving a traffic net with its main avenues, streets and highways. For the estimation of the emissions we developed a model that calculate the emission with a spatial resolution of 1km2 and generates hourly average emissions. The datas used for the calculation were: the vehicular flux evaluated in several places in Medellin in the period 1997 to 2000, number of cars by hour, type of vehicles, longitude of the tram of a way and emission factor for heat emission (we use a emission factor of CORINAIR study). As a result of the model, it was possible to determine the emission hour by hour of the pollutants analyzed in the each cells. A picture of the emission intensity shows that the downtown of Medellin represents the area more affected by the vehicular traffic, on-going in importance, the center-western region of the city. Likewise, for the analyzed area, the biggest emissions were evidenced in the hours of the day, with marked picks at 8:00 in the morning and 19:00 in the night. Future studies that involve local emission factors, obtained from own data of the region, become necessary to reach more representative results to the conditions of vehicular traffic in the Aburra valley.