This volume seeks to cover the latest scientific developments in the field of air pollution modeling. It contains papers and posters presented at the 26th NATO/CCMS International Technical Meeting on Air Pollution Modelling and Its Application held in Istanbul Technical University, Turkey, May 2003. Major topics covered include: the role of atmospheric models in air pollution policy and abatement strategies (air quality, risk assessment, emergency responses). Integrated regional modelling (local and urban effects, mesoscale phenomena, regional modelling, one and two way nesting, application of existing models). Global and long-range transport (synoptic, hemispheric & global scales, application of existing models). Aerosols as atmospheric contaminants (human exposure and health effects, direct and indirect climate effects, visibility reduction). New developments (microscale to global scale, new models, new extensions to existing models, inverse modelling, data assimilation). Model assessment and verification (model assessment, design of field experiments, use of on-site meteorological data, limits to predictability). Applications of new concepts in different regions of the world are also presented. The domain of the modeling covers all geographical sizes from global down to regional, local, urban and canyon sizes.