Nine new synthetic pyrethroids were tested as contact aerosols in a laboratory wind tunnel against field-collected adult female Anopheles quadrimaculatus Say and Psorophora columbiae (Dyar and Knab) in Arkansas. Propoxur and fenitrothion, potentially useful carbamate and organophosphorus adulticides, were also included in most of the tests. Malathion was included in all tests as a standard for comparison. In general, the pyrethroids were highly effective against both mosquito species. An exception to this high order of toxicity was noted with permethrin (3-phenoxyphenyl) methyl (+) Cis, trans - 3 - (2, 2- dichloroethenyl) 2, 2 -dimethylcyclopro- panecarboxylate) against Ps. columbiae, since it was only 2.1x more toxic than malathion against this species. Propoxur and fenitrothion were 2.6-5x more effective than malathion in these tests.