Byline: Ghasem Toloo (1), Gerard FitzGerald (1), Peter Aitken (2), Kenneth Verrall (3), Shilu Tong (1) Keywords: Heat warning system; Effectiveness; Mortality; Morbidity; Health beliefs; Health service utilization Abstract: Objectives To review the existing research on the effectiveness of heat warning systems (HWSs) in saving lives and reducing harm. Methods A systematic search of major databases was conducted, using "heat, heatwave, high temperature, hot temperature, OR hot climate" AND "warning system". Results Fifteen articles were retrieved. Six studies asserted that fewer people died of excessive heat after HWS implementation. HWS was associated with reduction in ambulance use. One study estimated the benefits of HWS to be $468 million for saving 117 lives compared to $210,000 costs of running the system. Eight studies showed that mere availability of HWS did not lead to behavioral changes. Perceived threat of heat dangers to self/others was the main factor related to heeding warnings and taking proper actions. However, costs and barriers associated with taking protective actions, such as costs of running air conditioners, were of significant concern particularly to the poor. Conclusions Research in this area is limited. Prospective designs applying health behavior theories should establish whether HWS can produce the health benefits they are purported to achieve by identifying the target vulnerable groups. Author Affiliation: (1) School of Public Health and Social Work, Queensland University of Technology (QUT), Victoria Park Rd, Kelvin Grove, Brisbane, QLD, 4059, Australia (2) School of Public Health, Tropical Medicine and Rehabilitation Sciences, James Cook University, Townsville, Australia (3) Environmental and Resource Sciences Division, Department of Environment and Resource Management, Queensland Government, Brisbane, Australia Article History: Registration Date: 20/03/2013 Received Date: 10/12/2012 Accepted Date: 20/03/2013 Online Date: 07/04/2013 Article note: This article is part of the special issue "Environment and Health Reviews".