This TECDOC presents the outcomes of international model validation exercises aimed at improving the performance of models used to assess radioactive contamination in urban environments. Building on the work of Working Group 2 under the MODARIA I programme, this intercomparison introduced models of greater complexity. The exercises addressed various scenarios, including dispersion and deposition events, short- and long-term redistribution of contaminants following deposition, and the evaluation of potential countermeasures or remediation strategies to reduce human exposure.