Given its importance for human health, vegetation, and the climate, the trends of ground-level ozone (O₃) concentrations in eastern Germany were systematically analysed making use of the long-term O₃ data from 16 measurement stations. The findings indicate that despite reductions in NO_x concentrations across all sites, O₃ pollution in Saxony has in fact worsened over the past 10 years, especially in densely populated urban areas. The strongest O₃ trend is observed at a traffic-dominated station, with an annual ozone increase of 1.2 &micro;g m^-3 year^-1 (or 3.5 % year^-1), while urban and rural background stations show more moderate rises, of, on average, 0.5 &micro;g m^-3 year^-1 (or 1.1 % year^-1) over the last decade.</p> <p>To diagnose O₃ formation and the controlling effects of NO_x and VOCs over the past decades in this target region, for the first time, detailed photochemical box modelling was performed by means of the complex MCM (Master Chemical Mechanism). Analysis of isopleth diagrams for two seasons indicates that O₃ formation was predominantly VOC-limited at traffic and urban sites from 2000 to 2019. The observed rise in O₃ levels suggests that current efforts to reduce total non-methane volatile organic compound (TNMVOC, including NMVOCs and oxygenated VOCs) emissions and NO_x from various sources unfortunately remain insufficient. Based on anthropogenic and biogenic emission data, we recommend that continued NO_x abatement and further additional VOCs controls, with a focus on solvent use, be implemented in densely populated areas to mitigate O₃ pollution in the coming years.