Five species of lichens, Ramalina fastigiata (Pers.) Ach., Ramalina capitata, (Ach.) Nyl., Ramaliana polymorpha (Lilj.) Ach., Ramalina pollinaria (Westr.) Ach., and Ramalina fraxinea (L.) Ach., belonging to family Ramalinacae were collected from middle Anatolia, Ankara, Antalya, Karabuk, and Kayseri in Turkey. Their usnic acid amounts were determined by HPLC in acetone extracts. Furthermore, antimicrobial activities of these extracts were determined against Escherichia coli (ATCC 35218), Enterococcus faecalis (RSKK 508), Proteus mirabilis (Pasteur Ens. 235), Staphylococcus aureus, Bacillus subtilis, and Bacillus megaterium. It was observed that, as the usnic acid amount increased, the antimicrobial activities were increased. Results pointed out that usnic acid contents of Ramalina species varied between 0.13% and 3.23% dry weight.