A global three-dimensional Lagrangian chemistry-transport model is used to describe the formation, transport and destruction of tropospheric ozone using 1990s global emissions and 1998 meteorological archives. Using a labelling technique, the geographical origins of the ozone formed within the troposphere have been revealed, showing whether the ozone found at the surface in Europe has had its origins above the continents of North America, Europe or Asia or elsewhere in the world. In this way, contributions to the ozone found at 21 surface monitoring sites across Europe can be attributed to production over North America and Asia, demonstrating that intercontinental ozone transport is an efficient process. Sensitivity tests to the global man-made sources of NOx and carbon monoxide indicate that global ozone precursor emission controls may contribute towards reaching regional air quality policy goals for ozone in Europe.