Paulinia and region constitute an important development center in the interior of Sao Paulo State, where there are several chemical industries and the largest petroleum refinery of Brazil. However, there are controversies related to air quality in this region. This work has as an objective the evaluation of air quality in this area by means of a mobile monitoring station, at the same time that the understanding of the relation source x receptor is looked for. The station has analyzers for SO2, H2S, NO, NO2, O-3, PM10, CO and total hydrocarbons (methane and non-methane) and a meteorological station. In a first stage (March to October 2000) the station was located in the campus of Unicamp, State University of Campinas, about 10 km distant from the main sources, to the Southeast. Comparing the results with Legislation CONAMA [1], it is observed that the primary limit for ozone (160 mug/m(3) - hourly average) was exceeded in one event in April, reaching a concentration of 167 mug/m(3). The other pollutants were found below their limits. In the second stage, beginning in November, 2000 and still in process in April, 2001, the station was located in Joao Aranha neighborhood, in Paulinia, approximately 5 km distant from the main pollutants sources, to the north-west. Analyzing the results in this period, it is verified that the primary limit for ozone was exceeded once in November, with the value equal to 162 mug/m(3). It is possible to conclude that in Paulinia and region, ozone must receive special attention, with the industries acting directly in precursors sources control. In general, the pollutants are well below their primary and secondary limits.