The essential oil from the aerial parts of Stachys cretica L. subsp. smyrnaea Rech. fil. (Lamiaceae), endemic to Turkey, was investigated by using GC and GC-MS. Thirty-four of 37 components, represented 99.7% of the total oil, were identified. The major components of the essential oil were trans-beta-caryophyllene (51.0%), germacrene-D (32.8%), a-humulene (3.1%), delta-cadinene (2.1%) and delta-elemene (2.1%). The antimicrobial activity of the essential oil, trans-beta-caryophyllene and five different extracts of the aerial parts of S. cretica L. subsp. smyrnaea were investigated by the standard disc diffusion method. The essential oil and trans-beta-caryophyllene exhibited antibacterial and antifungal activities. The activity increased with increasing concentrations of the essential oil and the extracts. The essential oil showed antimicrobial activity, particularly against Pseudomonas aeruginosa and Bacillus subtilis. The extracts exhibited either moderate or no activity.