A computer model for photochemical oxidant formation in the atmospheric boundary layer has been used to calculate trends in ozone formation in air masses traveling across Europe. Ozone calculations were made for some actual summertime anticyclonic weather episodes using air mass trajectories arriving at rural sites (Freiburg, southwest Germany and Nancy, northeast France) and sites close to more industrialized locations (Soltau, north Germany and De Bilt, Holland). The calculations suggest that, under these anticyclonic weather conditions ozone could build up relatively quickly to concentrations of >60 ppb even in rural areas. The highest levels calculated (130–150 ppb) were at distances ∼100 km downwind of major industrial areas. Transport of ozone could account for a significant proportion of the total ozone calculated at rural sites. A sensitivity analysis shows that high ozone levels are likely to occur despite large changes in precursor emissions of NOx, and volatile organic compounds (VOC).