 The Learning Health System Network, LHSN, is a collaboration between academic medical centres, healthcare systems, public health departments and health plans. It was established to facilitate outcomes research, pragmatic trials, comparative effectiveness research and evaluation of population health interventions. LHSN is one of 13 clinical data research networks assembled by the Patient Centred Outcomes Research Institute, COREY, to create a national patient-centred clinical research network. This network provides access to large amounts of real-world data from diverse populations, allowing researchers to conduct studies that are not possible in traditional clinical trial settings. In addition, it allows researchers to study how treatments work in different populations and how they interact with each other. This article was offered by L.J. Finney-Rutten, A. Alexander, P.J. M.B., and others.