Objective: The investigation of the chemical composition and antibacterial activity of essential oils from Teucrium polium and the chromosome number identification. Material and Methods: This study was carried in the Department of Biology and Ecology (University Ferhat Abbas) and ENSCCF (France) between September 2013 and October 2014. Aerial parts were collected from three localities from Eastern Algeria (Beni Aziz, Boutaleb and Amouchas). The air-dried aerial parts were subjected to hydro-distillation using a Clevenger-type apparatus. The analysis and identification of the essential oil components of Teucrium polium, was performed using the GC-MS. The disk diffusion method is utilised for determination of the antibacterial activity. Results: The average yield of essential oil of the samples is 0.37%. These analyses led to the identification of 57 components. The chemical composition of the essential oil of T. polium is dominated by the presence of a major product, α-pinene (14.1 - 18%), β-pinene (15.3 - 18.1%), germacrene-D (3.8 - 19%), myrcene (8.2 - 10.4%), limonene (5.3 - 8.7%), sabinene (2.7 - 4.3%), caryophyllene-(E) (1.8- 2.3%) and spathulenol (1 - 2.9%). The essential oil of the Beni Aziz population has a high antibacterial activity against Escherichia coli, Staphylococcus aureus and the yeast Saccharomyces cerevisiae. The population of Boutaleb has significant activity against Bacillus cereus and no action against S. aureus and the yeast S. cerevisiae. Conclusion: The observed differences and variability of the essential oil of T. polium of Algeria are likely due to different environmental and genetic factors. The number of components is different in these three populations of T. polium from eastern Algeria. Our investigation allows us to support the presence of several chemotypes in T. polium. The chemotype to germacrene-D is located in the regions of Amouchas and Boutaleb. Beni Aziz is the region that has favoured the development of Δ-elemene chemotype. The results of this work show that the essential oil of T. polium possesses antimicrobial properties, which can be used as natural antimicrobial agents.