Patients (and the communities they constitute) are the fundamental source of all clinical data. Much of the clinical data they generate emanates from clinic visits with health care providers. They also generate data from the pharmacies they purchase treatments from, the registries they participate in, and their use of modern/evolving technologies such as social media and wearables. In the setting of a traditional or telehealth-based encounter, clinical data in the form of laboratory test results, imaging, and notes are all generated and housed with an EHR system. These data may be repackaged and sent to managed care organizations and health care payors to facilitate reimbursement. These payors also transmit data relevant to drug benefits to pharmacy benefit managers (PBMs), who negotiate payment for drugs dispensed in pharmacies. Quality data from the EHR are also used by accountable care organizations (ACOs) to support certain quality-based reimbursement schemes. EHR data are also consumed by clinical researchers, individuals who oversee health care operations, and data aggregators. The latter deidentify and repackage these data for consumption by a variety of parties, including biopharmaceutical companies and regulators, as relevant for monitoring of treatment safety and efficacy, among other uses. Although most patient data represent a form of RWD, some patient data are collected in the setting of controlled trials. Although data from cardiac devices (e.g., pacemakers/cardioverter-defibrillators) and glucose meters occasionally end up in the EHR, data from consumer wearables and sensors and social media are currently not integrated into EHR systems. However, these data are increasingly being studied for their potential utility in health care, and may be integrated in the future. Adapted with permission from Datavant (58).