It has long been known that herbs and their extracts have an antimicrobial activity. Sideritis ozturkii Aytac & Aksoy and Sideritis caesarea Duman, Aytac et Baser endemic plant species for Turkey have been traditionally used as medicinal tea and spice in different regions of Turkey especially the Mediterranean and the middle part of Anatolia. In this study, total phenolic, flavanol and flavonol compounds of the methanolic extracts of S. ozturkii and S. caesarea, and their antimicrobial and antioxidant effects were determined. Total phenolics and total flavonol contents of S. caesarea extract were higher than those of S. ozturkii extract. Antioxidant activities of the extracts tested by the DPPH radical scavenging system were 41.68 +/- 31.96% and 72.47 +/- 0.73 % at 100 ppm concentration of S. ozturkii and S. caesarea extracts, respectively. Antimicrobial activity was assessed by the agar diffusion method against fifteen microorganisms. In conclusion, it can be said that the extracts of S. ozturkii and S. caesarea could be used as natural antimicrobial and antioxidant agents in the food preservation and human health. (C) 2007 Elsevier Ltd. All rights reserved.