Field efficacy trials comparing 2 formulations of deet against mosquitoes in Redcliffe, Queensland, Australia were conducted in February 2009. A formulation containing 35% deet in a gel (Australian Defence Force deet) provided >95% protection for 3 h, while a formulation containing 40% deet in ethanol (Bushman) in a spray applicator provided >95% for 6 h. A user acceptability study showed that 82% of soldiers using the Bushman formulation during contingency operations for 14–28 days in Timor–Leste would recommend this formulation to others and believed that the formulation provided protection against mosquitoes.