The aerial parts of four populations of Salvia mirzayanii were collected from different natural habitats of Fars province in southwest of Iran. Chemical composition of S. mirzayanii were isolated by hydrodistillation using Clevenger type apparatus and analyzed by GC-FID and GC/MS. The major compounds in four population were α-terpinyl acetate, eudesm-7(11)-en-4-ol, bicyclogermacrene, δ-cadinene, 1,8-cineole, germacrene D-4-ol , cis-dihyroagarofuran , linalyl acetate, α-cadinol , linalool and α-terpineol in four ecotypes. The in vitro antimicrobial activity of the essential oil of different ecotypes of S. mirzayanii were studied against Staphylococcus aureus, Escherichia coli and Candida albicans by disc diffusion method. The results showed that the oil exhibited good antimicrobial activity against all medically important pathogens. [ABSTRACT FROM AUTHOR]