Laboratory tests were conducted to study the response of Anopheles dirus and Aedes albopictus to repellent formulations containing diethyl methylbenzamide (deet) and dimethyl phthalate. Anopheles dirus was tolerant of low concentrations of deet (5-20%), and formulations containing < or = 35% deet provided protection for < or = 90 min. In contrast, Ae. albopictus was sensitive to these formulations, which provided > or = 180 min protection from bites.