Hundreds of thousands of dengue cases are reported worldwide each year. Given the difficulty in obtaining full reporting, the actual number of human infections is probably much higher than the number reported. Dengue is usually a nonspecific febrile illness that resolves with supportive therapy but the clinical spectrum ranges from asymptomatic infection through severe hemorrhage and sudden fatal shock. The pathophysiology of the severe forms of dengue may be related to sequential infection with different serotypes, variations in virus virulence, interaction of the virus with environmental and host factors or a combination of these factors. Control of dengue at the present time is dependent on control of the principal vector mosquito, A. aegypti. Efforts to achieve such control are now focusing on community education and action towards eliminating this mosquito's breeding sites near human dwellings. Vaccine development continues, but at present the only way to avoid dengue in an area where it is endemic or epidemic is to use repellents and mosquito barriers. The movement of people to and from tropical areas makes dengue an important differential diagnosis in any patient with an acute illness and history of recent travel to tropical areas. Because of continued infestation of the southeastern United States with A. aegypti, indigenous transmission in the continental United States remains a public health concern.