Shoalwater Bay military training area (SWBTA), 2,713 km² of land located 50–80 km north of Rockhampton, Queensland, Australia, is used by Australian and allied forces for training purposes. Between March 1998 and February 2000, monthly collections of mosquitoes at 15 sites were conducted using carbon dioxide-baited traps to study the seasonal occurrence of mosquitoes and Ross River virus (RRV) and Barmah Forest virus (BFV) in mosquitoes. A total of 72,616 mosquitoes, comprising 3,897 pools were collected, and 2,428 pools were tested using a reverse transcriptase-polymerase chain reaction. A total of 15 pools of mosquitoes were positive for virus, 10 RRV and five BFV. Blood meals from an additional 763 mosquitoes were tested by a gel diffusion assay, and the majority (96%) of those identified were from kangaroo, which was the most common mammal in the study area. The results indicate that Culex annulirostris Skuse and Ochlerotatus vigilax (Skuse) are the main vectors of RRV at SWBTA.