Abstract A hydrodistilled oil from the leaves of Teucrium mascatense Boiss. was analyzed by GC/MS. Twenty-one components amounting to 91.2% of the oil were identified with linalool (27.8%), linalyl acetate (12.6%) and Î²-eudesmol (10.1%) being the major constituents of the oil. The antimicrobial activity of the oil was tested against a panel of 17 bacterial and six fungal strains by the disc diffusion method. The oil inhibited the growth of all test organisms at various levels. The minimal inhibitory concentrations (MIC) were also determined. Key Word Index: Teucrium mascatensis Lamiaceaeessential oil compositionlinaloollinalyl acetateÎ²-eudesmolantimicrobial activity