The efficacy of monomolecular organic surface films of isostearyl alcohol containing 2 oxyethylene groups was evaluated at varying dosages against natural populations of Aedes taeniorhynchus Wiedemann in several salt-marsh habitats. Results of ground and aerial spray application at surface dosages of 0.30 - 0.45 mn/m2 (0.32 - 0.48 gal/acre) indicated that this chemical can be used effectively to control larvae and pupae of this Aedes sp. under a wide range of field conditions. Methodology for field application, mode of action of this chemical on immature mosquitoes, and environmental factors which influence the surface-film method are discussed.