The National Notifiable Diseases Surveillance System (NNDSS) received 8,671 notifications of diseases transmitted by mosquitoes in Australia for the season 1 July 2007 to 30 June 2008. This represented a 39% increase from the annual average of 6,259 notifications for the previous 5 years. The alphaviruses, Barmah Forest and Ross River, accounted for 7,760 (89%) of these notifications during the 2007/08 season and represents an increase when compared with the mean of the past 5 seasons. Detection of flavivirus seroconversions in sentinel chicken flocks across Australia provides an early warning of increased levels of Murray Valley encephalitis virus (MVEV) and Kunjin virus activity. Unusual MVEV activity in mosquitoes and sentinel chicken flocks was reported in southeast Australia during the 2007/08 season. Two cases of MVEV were reported, one each from New South Wales and Western Australia. There were 365 notifications of dengue virus infection that were acquired overseas compared with an average of 164 overseas-acquired dengue cases per annum reported to NNDSS over the 5 seasons from 2002/03 to 2006/07. There were no reports of locally-acquired malaria notified in Australia and 505 notified cases of overseas-acquired malaria during the season 2007/08. The exotic dengue vector Aedes aegypti was first detected on Groote Eylandt, Northern Territory in October 2006 and led to a 2-year Ae. aegypti eradication project. The successful eradication of Ae. aegypti from Groote Eylandt was officially announced in May 2008. The success of the program was due to the selection of appropriate chemicals that were successful in treating mosquito adults, larvae and egg infested receptacles. This annual report presents information on diseases transmitted by mosquitoes in Australia and notified to NNDSS.