This article defines the key components of a "rapid response system" (RRS), which the authors propose as a unifying term for medical emergency teams, rapid response teams, and other similar teams designed to intervene on clinically unstable inpatients. An RRS should consist of an "afferent limb," the mechanism by which team responses are triggered; an "efferent limb," the team of clinicians that responds to an event; an administrative arm responsible for team staffing, education, and implementation; and a quality improvement arm to assess effectiveness of the RRS and identify underlying quality of care issues. RRS effectiveness should be monitored by measuring mortality, cardiac arrests, and unplanned intensive care unit admissions. The authors did not endorse a specific model for the efferent limb, stating that physician-led or nurse-led models may both be appropriate depending on local circumstances. No consensus was reached on whether all hospitals should be mandated to institute an RRS.