A study comparing the effectiveness of barrier treatment of military tents with bifenthrin and permethrin in preventing entry of mosquitoes was conducted at Wide Bay Training Area, Queensland, Australia. Five military tents were erected at a site in bushland at Mosquito Creek, about 2 km from the coast. Two tents were sprayed with bifenthrin (Bistar 80SC, 0.1% mix, 12.5 ml/liter) and 2 with permethrin (Perigen 500, 1.2%, 24 ml/liter). One was left untreated and served as a control. Carbon dioxide-baited traps were placed inside each tent 0, 2, 4, 6, and 8 wk after treatment, and a single trap was placed in forest 50 m from the tents. The predominant mosquito species collected was Aedes vigilax (78% of collection). Compared to the untreated control, protection against mosquitoes entering treated tents was initially 78.6% for bifenthrin-treated tents and 84.3% for permethrin. At 4 wk, protection was 68.6% for bifenthrin and 50.7% for permethrin. After 6 wk, less than 34% protection was provided by either insecticide. There was no significant difference between the protection provided by either insecticide treatment. The study showed that barrier tent treatments provide a reasonable increase in preventing the entry of mosquitoes for at least 4 wk.