Bioassay-guided chemical investigation of the roots of Anthriscus sylvestris (L.) Hoffm. resulted in theisolation of nine compounds, whose structures were determined by spectroscopic methods. Compound 1 wasisolated from this plant for the first time and compounds 3 and 9 were first found from this genus. Differentpolar fractions of A. sylvestris extract and compounds 1, 6-8 and 9 were evaluated for antitumor activities againstHepG2 (human hepatocellular carcinoma), MG-63 (human osteosarcoma cells), B16 (melanoma cells) and HeLa(human cervical carcinoma cells) lines by the MTT method. The petroleum ether fraction of A. sylvestris extractexhibited excellent inhibitory activity with an IC50 value of 18.3 μg/ml. Among the isolates from the petroleumether fraction, compound 7 showed significant inhibition against the growth of the four tumor cells with IC50values ranging from 12.2-43.3 μg/ml.