Anopheles quadrimaculatus Say and Psorophora columbiae (Dyar and Knab) adults were exposed to various rates of permethrin residues to determine the effective dosage range as well as duration of activity. One ft2 plywood panels were treated with permethrin at concentrations ranging from 0.0625 to 3.0 grams Ai/m2 standard (malathion 1 g/m2) was also included. One set of panels was maintained in indoor (lab) conditions, and one set was exposed to all outdoor elements except rainfall. The effective indoor and outdoor rates over the 11-week test period were ca 0.125 and 0.50 grams. Ai/m2 respectively for both mosquito species. An. quadrimaculatus appeared to be slightly more susceptible than Ps. columbiae to residues maintained in outdoor conditions; however, more recovery from the 1-hour knockdown occurred with lower dosages in both situations. Malathion was not as effective as permethrin against either species, especially An. quadrimaculatus, under outdoor conditions.