Tests were conducted to determine the persistence of compounds applied to tents to protect against mosquitoes. Interiors of 2 camping tents were treated by the manufacturer--one with the repellent dimethyl phthalate (DMP) and one with the insecticide permethrin. A third tent was untreated. Tents were set up outdoors and exposed to weathering for one year. Weekly tests were conducted by releasing Aedes aegypti into the tents, then recording knockdown (KD) and biting behavior during a 3-h period. Weather data were collected 24 h/day during the study. Year-long mean KD of mosquitoes exposed in the tent to permethrin was 58.6%, to DMP 2.7% and the control 0.9%. Mean biting was 11.9, 43.8 and 58%, respectively. Under constant exposure to weathering, the permethrin-treated tent gave best results with average protection from bites greater than 96% for 9 months (DMP was less than 31%). Although preliminary, the data suggest permethrin would be effective as a tent treatment to reduce annoyance of mosquitoes.