The aerial parts of Ziziphora clinopodioides, Cyclotrichium niveum, and Mentha longifolia ssp. typhoides var. typhoides were screened for their possible antioxidant and antimicrobial activities in addition to their penolic contents. Antioxidant activity was employed by two complementary test systems: 2,2'-diphenyl-1-picrylhydrazyl free radical scavenging and beta-carotene/linoleic acid. In the first case, Z. clinopodioides was superior to the other species with a 50% inhibitory concentration value of 37.73 +/- 1.18 mu g/mg. Similar results were obtained from the b- carotene/linoleic acid system. Inhibition capacity of the linoleic acid of Z. clinopodioides was 83.56 +/- 1.19%. Additionally, antioxidant activities of butylated hydroxytoluene, curcumin, and ascorbic acid were determined in parallel experiments. Methanol extracts obtained from the plants studied were found to have moderate antimicrobial activity against all microorganisms tested. In general, Z. clinopodioides extract exhibited stronger activity than the other extracts. On the other hand, Acinetobacter lwoffii and Candida krusei were the most sensitive microorganisms for the all extracts. The amount of the total phenolics was highest in Z. clinopodioides extract (129.55 +/- 2.26 mu g/mg),followed by M. longifolia ssp. typhoides var. typhoides (93.47 +/- 1.84 mu g/mg). It is extremely important to note that there is a positive correlation between antioxidant activity potential and amount of phenolic compounds.