ULV applications of technical malathion (0.15–0.58l/ha), using a Cessna 300B Agwagon fitted with four AU 3000 Britten Norman Micronair units, gave satisfactory control of mosquitoes (Aedes taeniorhynchus) in mangrove swamp habitats on Grand Cayman. Spraying began just prior to sunset when conditions were most suitable. Using swath widths of 182 m, 1600 ha could be sprayed in one sortie. The vmd of the droplets in all trials was between 56–92 μm for outputs of 3.8–15.2l/min. Between 0.07 and 0.58l/ha the mean number of droplets varied between 8 and 34/cm2. After applications of 0.15–0.58l/ha light trap and vehicle operated cone trap mosquito counts were reduced. Satisfactory reductions of mosquitoes occurred after an application of 1% synergised pyrethrum in diesoline (0.73l/ha). Spraying 0.5% bioresmethrin in diesoline at 0.73l/ha initially reduced mosquito numbers considerably, but a brood of adults emerging immediately after spraying compensated for the losses.