Abstract The chemical composition of the volatile fractions obtained by steam distillation from the whole aerial parts, capitula and stem+leaves of Mantisalca duriaei Briq. et Cavill was analyzed by GC and GC/MS. Thirty-six constituents were identified. Methyl hexadecanoate (18.8%), farnesyl acetate (17.6%), docosane (9.1%) and methyl linolenate (9.4%) were found to be the main components in the whole aerial parts. This latter was the major compound in the flowers (42.6%) while methyl hexadecanoate (38.3%) and methyl linolenate (22%) were the main components in the stems+leaves. Furthermore, the oils were tested against six Gram-positive and Gram-negative bacteria and four phytopathogenic fungi. The Mantisalca duriaei oils exhibited an interesting antibacterial activity against all strains tested except Pseudomonas aeruginosa but no antifungal activity was detected. Key Word Index: Mantisalca duriaei Asteraceaeessential oil compositionmethyl hexadecanoatemethyl linolenatefarnesyl acetateantimicrobial activity