Methanolic extract of Satureja kitaibelii Wierzb. ex Heuff. (Lamiaceae) and its major compond rosmarinic acid possessed strong antimicrobial activity against tested bacteria and fungi, and antitumour activity against malignant cells, but without antiproliferative effect on healthy cell line MRC5. Minimal inhibitory concentration (MIC) of methanolic extract was ranged between 0.0125-1.25 mg/ml, while minimal bactericidal concentration (MBC) was of 0.2-5.0 mg/ml and fungicidal (MFC) was 0.15-2.5 mg/ml. The rosmarinic acid exhibited better antimicrobial activity then methanol extract. The most sensitive species to rosmarinic acid were Bacillus cereus and Candida kruzei, while Micrococcus flavus, Trichoderma viride and Aspergillus niger were the most resistant. The methanol extract exhibited strong activity against Fem-x human malignant melanoma cells with an IC50 39.66 +/- 2.71 mu g/ml, and moderate activity against other cancer cell lines (IC50 from 138.06 +/- 0.16 mu g/ml against estrogen-dependant breast cancer cell lines MDA-MB-361 to 173.15 +/- 0.02 against a human epithelial cervical cancer cells HeLa). Rosmarinic acid arrested G2/M phase cell cycle in Fem-x cells, against which both methanol extract and rosmarinic acid possessed the best cytotoxic activity