Patient-reported outcome (PRO) is an "umbrella term" that covers a whole range of potential types of measurement but it is used specifically to refer to all measures quantifying the state of health through the evaluation of outcomes reported by the patient himself/herself. PROs are increasingly seen as complementary to biomedical measures and they are being incorporated more frequently into clinical trials and clinical practice. After considering the cultural background of PROs - that is the well known patient-centered model of medicine -, their historical profile (since 1914, the year of the first outcome measure) and typologies, the paper aims at debating their methodological complexity and implementation into practice. Some clinical trials and therapeutic managements utilizing patient-centered measures will be also analyzed.