The cotton aphid, Aphis gossypii Glover, is an important pest of a number of field and greenhouse important crops in all around the world. In recent years, the use of essential oils derived from aromatic plants has been considered as low-risk insecticides. Essential oils have repellent, insecticidal and growth-reducing effects on a variety of insects. The objective of the present work was to determine the potential of some essential oils against A. gossypii as repellent, fumigant and contact insecticides and to charactrize their composition by GC-Mass analysis. The phytotoxicity of essential oils formulations were also determined on the cucumber leaves. The fumigant toxicity of 20 essential oils were investigated in the screening test against Aphis gossypii adults at three concentrations (1.4, 11.7 and 23.5 µl L -1 ). Thirteen essential oils with the highest activity at concentration of 23.5 µl L -1 were chosen for adult fumigant bioassay. Seven essential oils with the LC 50 values of lower than 11 µl L ?1 for adults were selected for fumigant bioassay on the third and first numphal instars, contact toxicity, repellency bioassay and phytotoxicity test. The main constituents of the essential oils of Mentha pulegium, Cuminum cyminum, Mentha piperita, Mentha spicata, Ferula gummosa, Anethum graveolens and Myrtus communis were pulegine, cuminylaldehyde, menthole, carvone, ?-pinene, ?-phellandrene and 1,8-cineole, respectively. In the fumigant bioassays, for adult aphids, the essential oil of M. pulegium was the most toxic (LC 50 = 4.70µl L ?1 ), followed by oils from C. cyminum (LC 50 = 4.87 µl L ?1 ), M. piperita (LC 50 = 5.08 µl L ?1 ), M. spicata (LC 50 = 5.24µl L ?1 ), F. gummosa (LC 50 = 5.83µl L ?1 ) , A. graveolens (LC 50 = 7.94µl L ?1 ), Eucalyptus globelus . (LC 50 = 9.24µl L ?1 ), Lavendula stoechas (LC 50 = 9.33µl L ?1 ) , M. communis (LC 50 = 10.72µl L ?1 ) , Foeniculum vulgare (LC 50 = 16.60µl L ?1 ), Zataria multiflora (LC 50 = 19.79µl L ?1 ) , Pelargonium roseum (LC 50 = 23.42µl L ?1 ) and Matricaria chamomila (LC 50 = 24.59µl L ?1 ). The LC 50 values of fumigant toxicity of essential oils against third-instar nymph and first-instar nymph were M. pulegium (LC 50 = 2.13 and 1.43µl L ?1 ), C. cyminum (LC 50 = 3.20 and 1.82 µl L ?1 ), M. spicata (LC 50 = 3.41and 2.70µl L ?1 ), M. piperita (LC 50 = 3.78 and 1.65µl L ?1 ), A. graveolens (LC 50 = 4.41and 3.21 µl L ?1 ), F. gummosa (LC 50 = 5.56 and 4.06 µl L ?1 ) and M. communis (LC 50 = 7.05 and 5.66µl L ?1 ), respectively. The LC 50 values of formulations in the contact bioassay for C. cyminum , M. pulegium , M. piperita , M. picata , A. graveolens , F. gumosa and M. communis were 9045, 10497, 13620, 14033, 18221, 18685 and 22310 mg L -1 , respectively. The repellency bioassay showed that all tested formulations with the exception of M. piperita and M. spicata formulations has a repellent effect on aphid adults. F. gommosa caused high repellency effect (68.75%) on adult aphids. All tested formulations of essential oils at the highest tested dose caused some phytotoxicity on the cucumber leaves. Due to the high efficiency of the tested essential oils in this study by further studies on the finding appropriate formulations, it will be possible to use them against the aphids in the near future. Key Words: Essential oils, Pesticide formulation, Botanical insecticides, Insecticidal effect, Cotton- melon aphid