This paper describes how transportation noise makes the largest contribution to environmental noise. The European Directive 2002/49/EC relating to the assessment and management of environmental noise requires European Union (EU) Member States to assess and reduce environmental noise by means of noise mapping and subsequent action plans (to manage noise issues and effects) for roads, railways, airports and urban agglomerations. The agglomeration of Bologna, Italy, consists of the Municipality of Bologna and four other smaller municipalities, overall accounting for more than 450 000 inhabitants. It includes some major highways, railways and a national airport. The regional Authority, Regione Emilia- Romagna, assigned the task to fulfil the END to DIENCA. This paper describes the organization and methods implemented to make the strategic noise mapping of the agglomeration of Bologna, reporting on the man problems encountered, e.g. the harmonization of data coming from different sources, the selection of a digital ground model suited for the subsequent acoustic simulation, etc. , and the ways to solve them. The overall noise maps of the agglomeration of Bologna are presented. Some remarks about the accuracy of predictions and the main sources of uncertainty are also presented in the paper.