Peels of citrus species from Argentina and the United States were subjected to hydrodistillation to obtain their essential oils. Gas chromatography/mass spectrometry was carried out to determine the chemical composition of all the essential oils. Limonene was found as the major compound with many minor components varying according to the different species. Antioxidant assays were done to determine the antioxidant activities of essential oils. The antimicrobial activity was tested against Leuconostoc mesenteroides MS1, Escherichia coli ATCC 25922 and Lactobacillus plantarum ES147 and ATCC 8014. Mandarin essential oil from the USA showed the strongest antioxidant capacity in different assays. Grapefruit and lemon essential oils showed consistently strong antimicrobial activity against all tested bacteria, so they were selected for determining the minimum inhibitory concentration and minimum bactericidal concentration values against E. coli ATCC 25922 . Minimum inhibition concentration values ranged between 0.33 and 0.55 mg/mL and minimum bactericide concentration values ranged between 0.42 and 0.95 mg/mL.Fil: Vignola, María Belén. Universidad Tecnológica Nacional. Facultad Regional San Francisco. CONICET; Argentina.Fil: Raspo, Matías A. Universidad Tecnológica Nacional. Facultad Regional San Francisco. CONICET; Argentina.Fil: Andreatta, Alfonsina E. Universidad Tecnológica Nacional. Facultad Regional San Francisco. CONICET; Argentina.Fil: Juliani, H. R. New Use Agriculture and Natural Plant Products Program, Department of Plant Biology, School of Environmental and Biological Sciences (SEBS) Rutgers University, New Brunswick, NJ, 08901, USAPeer Reviewed