A biochemical characterization and a geographic variability of Thymus capitatus L. essential oils were undertaken. Chromatographic analysis using gas chromatography-ï¬ame ionization detector and gas chromatography-mass spectrometry of essential oils extracted from thyme aerial parts from four Tunisian regions (Kef, Bizerte, Boukornine and Grombalia) showed the predominance of carvacrol (75.79 ± 2.07%) in Boukornine region, thyme essential oils being carvacrol chemotype. Obtained results of antimicrobial activities showed that thyme essential oil has important antibacterial activity which was strongly related to the organoleptic quality of the oil which appeared strongly region-dependent. The inhibitory effect of thyme essential oils on the bacteria and fungi development showed that Bacillus cereus and Fusarium solani were the most sensitive bacteria and fungi, respectively. From these results, we have concluded that thyme essential oil could be used to cure mycotic infections and may have role as pharmaceutical and preservative agents.