Adherence to drug therapies is an essential and cross matter for the management of chronicity. The concept of adherence, over time, has changed, with consequences on terminology, in order to emphasize the active role of the patient, as a key element for the success of the treatment process. Poor adherence to chronic therapies, if appropriate, is known to have repercussions both in terms of health and economic outcomes. However, there are complex and various barriers that prevent the achievement of optimal adherence and that require multifactorial, relational and organizational solutions to be eliminated. In this sense, the role of health data is strategic which, if properly analysed, make it possible to identify the target of improvement interventions, to quantify their effect and evaluate their health outcomes and economic savings. Further research, of excellent quality, collaborative and rigorous, is needed to identify the rules and methodologies for measuring adherence, to identify possible improvement strategies, in order to include them within the care pathways. To reach these objectives a Working Group of the MaCroScopio Project was held, whose reflections have been collected in this dossier.