Rapid response systems (RRSs) are one of the first organisation-wide, patient-focused systems to be developed to prevent potentially avoidable deaths and serious adverse events such as cardiac arrests. RRSs identify seriously ill and at-risk patients and those whose condition is deteriorating, using abnormal vital signs and observations that trigger an urgent response by staff who are able to deal with any medical emergency. RRS teams also respond to staff concern--any bedside nurse or doctor who is concerned about his or her patient can seek assistance. RRSs require the support of the whole hospital. This includes resources, educational programs and agreed ways of evaluating RRS effectiveness. RRSs may reduce deaths by up to one-third and cardiac arrests by up to 50%.