The present study was conducted to evaluate the antioxidant and antitumor activities of the essential oil and ethanolic extract of thyme (Thymus vulgan's) leaves The antioxidant test results showed that the essential oil strongly reduced the thiobarbituric acid (TBA) values at 100, 200, 400 and 1000 ppm concentrations and it was more effective than thymol and BHT at a concentration of 1000 ppm. The ethanolic extract was able to reduce the TBA values, which were lower than those of essential oil, thymol and BHT The viability of Ehrlich ascites carcinoma cells (EACC) with essential oil and ethanolic extract at different concentrations was examined. it was found that incubation of tumor cells with essential oil reduced the viability of these cells and the dead cells produced by this oil reached 100% by concentrations over 200 ppm, while the ethanolic extract was lower than essential oil compared with thymol. Also, effect of essential oil and thymol at concentrations of 200 and 400 ppm on the survival of tumor bearing mice in the same time and after a week of injection with EACC was studied. The essential oil gave a higher cytotoxic effect than thymol whereas different treatment showed significant increase in the life span of tumor bearing mice compared with untreated tumor control. _ The chemical composition of essential oil and ethanolic extract were analyzed by GC and HPLC. The essential oil comprised of 18 constituents representing 91.42% of the oil. Carvacrol (28.98%), limonene (25.17%), 7 - terpinene (10.86%), terpeniol (9.73%), [3- caryOphyllene (7.81%), linalool (2.83%) and thymol (2 12%)were the major components comprising 84.64% of the oil. The ethanolic extract was analyzed by HPLC system. Data showed that T vuigaris characterized by the presence of a high content of p-coumaric acid (39.80%), vanillin (24.34%) and moreover. caffic acid (5.09%) and Ferulic acid (4.04%) were also detected Results presented here may suggest that the essential oil of T. vuigari's can be used in pharmaceutical industries for its potential medicinal properties including antioxidant, protective and anticarcinogenic effects.