Climate change factors such as elevated CO2 concentrations, warming and changes in precipitation affect the stomatal flux of ozone (O-3) into leaves directly or indirectly by altering the stomatal conductance, atmospheric O-3 concentrations, frequency and extent of pollution episodes and length of the growing season. Results of a case study for winter wheat indicate that in a future climate the exceedance of the flux-based critical level of O-3 might be reduced across Europe, even when taking into account an increase in tropospheric background O-3 concentration. In contrast, the exceedance of the concentration-based critical level of O-3 will increase with the projected increase in tropospheric background O-3 concentration. The influence of climate change should be considered when predicting the future effects of O-3 on vegetation. There is a clear need for multi-factorial, open-air experiments to provide more realistic information for O-3 flux-effect modelling in a future climate. (c) 2006 Elsevier Ltd. All rights reserved.