The World Health Report 2000 on the performance of health systems posited responsiveness to citizens' expectations as a central and particular goal. It pushed forward a debate that framed responsiveness as a valued and desired outcome of health system interventions regardless of the extent to which those interventions lead to health improvement. Health services reforms in many countries thus place ever increasing emphasis on meeting citizens' expectations, improving responsiveness to patients and increasing both population and patient satisfaction. This chapter first explores the basic concepts behind patients' and citizens' experience, namely satisfaction, responsiveness, experience and related terms. It then consider the major approaches and actors to measure them and discuss indicators and available data.