We describe an experiment that shows the importance of convection in long-range transport of air pollutants and in enhancing upper tropospheric ozone production. A research flight was conducted during clear-sky summertime conditions over north-central Oklahoma and central Kansas to measure vertical profiles of CO, O3, reactive nitrogen compounds, and a variety of meteorological variables. Correlation analyses were conducted on the profiles of pairs of the trace gases to infer source of these gases. Areas of ozone predominantly produced photochemically in the troposphere and smaller areas with ozone of primarily stratospheric origin were identified. Meteorological analyses indicated that increased CO and NOy concentrations found at high altitude were carried by convective clouds from the boundary layer to the upper troposphere. High levels of ozone precursors were still discernable a great distance (600 km) downwind. Net O3 production was computed for the lower and upper troposphere, while net destruction was computed for the midtroposphere, where NO levels were very low. ¿ American Geophysical Union 1989