Propoxur I MOS was diluted with No. 2 fuel oil and applied by air for adult mosquito control (mostly Aedes vexans and A. sollicitans). Applications of 0.5 and I oz AI per acre were applied in a volume of 32, 24 and 12 fluid ounces per acre by adjustment of the dilution ratio or by varying the swath width. A greater initial mosquito reduction was recorded at 0.5 oz AI acre applied over an open area than I oz AI per acre applied over areas with dense foliage. Control for the low rate ranged from 88% at 1 hr post-treatment to 98% at 24 hr post-treatment compared with 40% at 1 hr post-treatment and 91% at 24 hr for the high rate. The volume applied had no effect on the results.