The chemical composition of hyssop oil from Bulgaria was determined by gas chromatography with flame ionization detection and gas chromatographymass spectrometry on two different chromatographic columns. The quantity of identified compounds was shown correspond to 97.2% and 98% of the total oil content. Among the detected compounds,
cis-pinocamphone (48.98%-50.77%), β-pinene (13.38%-13.54%), trans-pinocamphone (5.78%-5.94%) and β-phellandrene (4.44%-5.17%) were the major compounds. Hyssop oil demonstrated antifungal activity against 52 clinical isolates and reference strains of Candida albicans, Candida glabrata, Candida tropicalis, Candida parapsilosis and Candida krusei. The essential oil characterized with stronger antifungal activity in comparison with pure cis- and trans-pinocamphone, α- and β-pinene and β-phellandrene. Essential oil of Hyssopus officinalis L. from Bulgaria inhibited both fluconazol-sensitive and fluconazol-resistant strains.