Dipterocarpaceous plants contain various resveratrol oligomers that exhibit a variety of biological activities, such as antibacterial and antitumor effects. Previously, we found that vaticanol C, a resveratrol tetramer, exhibits strong cytotoxicity against various tumor cell lines. In the present study, we examined the antitumor activity of the ethanol extract from the stem bark of Vateria indica, which has been traditionally used for health and healing diseases as Ayurveda in India. High-performance liquid chromatography analysis showed that the extract contains bergenin, hopeaphenol, vaticanol B, vaticanol C, and epsilon-viniferin. The in vitro assay displayed the extract's anti-cancer activity against mouse sarcoma 180 cells (IC50=29.5 microM). In the animal study, the tumor growth of sarcoma S-180 cells subcutaneously allografted in DDY mice was significantly retarded by oral administration of the extract (30 or 100 mg/kg body weight: P < 0.001). The extract did not show significant toxicity to mice even at a dosage of 1000 mg/kg body weight by daily oral administration for 28 days. These results demonstrated that the ethanol extract containing various stilbenoids from the stem bark of V. indica has the potent antitumor activity.