The special issue aims to reflect on the usability and relevance of mobile phone traffic data for territorial research, on the challenges posed by its treatment in statistical terms, and on possible integration with other available datasets, presenting the outcomes of specific empirical experiments on three territorial settings (Milan, Lecce and its coast and the Piacenza Apennines). These settings represent relevant and challenging study contexts within research on territorial fragilities carried out by the Department of Architecture and Urban Studies, Politecnico di Milano, in the last few years. Processing mobile phone data in these three Italian cases, characterized by different socio-territorial conditions, settlement densities, and mo...