This study was designed to examine the chemical compositions and antimicrobial activities of the essential oils from Cladonia rangiformis Hoffm. and Cladonig furcata (Huds.) Schrad. The essential oils were isolated by hydrodistillation and analyzed with GC and GC-MS and screened for their in vitro antimicrobial activity in a microdilution assay. In total, 25 and 12 compounds were identified from the oil of C. rangiformis and C. furcata, accounting for 89.2 % and 91.6 To of the detected GC peak areas, respectively. The essential oils consisted mainly of alcohols (29.4 % and 1.6 %), ketone (21.7 % and 18.6 %) and hydrocarbons (13.1 % and 57.6 %). The major compound of the essential oils was 3-octanone (21.7 % and 18.6 %), respectively. The inhibitory effects of the essential oils of C. rangtformis and C. fiircata, were tested against seven bacterial species using the disc-diffusion method and C. rangifonnis oil exhibited the antimicrobial and antifungal activity against Enterococcus faecalis and Candida albicans (MIC = 306.2 mu g/mu L, each), whereas, C. fiurata oil showed only antifungal activity against the pathogenic yeast C. albicans (MIC = 784.4 mu g/mu L).