Autochonous dengue infections were last reported Hawaii in 1944. In Septembber 2001,the Hawaii Department of health was notified of an unusual febrile illness in a resident with no travel history; dengue fever was confirmed.During the investigation,1,644 persons with locally acquired denguelike illness were evaluated,and 122 (7%) laboratory-positive dengue infections were identifed;dengue virus serotype 1 was isolated from 15 patients.No cases of dengue hemorrhagic fever or shock syndrome were reported.In 3 instances autochthonous infections were linked to French Polynesia.Phylogenetic analyses showed the Hawaiian isolates were closely associated with contemporaneous isolates from Tahiti.Aedes albopictus was present in all communities survyed on Oahu,Maui,Molokai,and Kauai;no Ae. aegypti were found. This outbreak underscoores the importance of maintaining surveillance and control of potential disease vetors even in the absence of an imminent disease threat