From the chemical investigation of the methanolic extract of the roots of the Thai dipterocarp, Dipterocarpus tuberculatus, two new oligostilbene glycosides, dipterostilbenes A (1) and B (2), were isolated together with four known stilbenes. Their structures and relative configurations were determined on the basis of spectroscopic data. From an evaluation of cytotoxic activity against KB and HeLa cell lines, α-viniferin (5) and (-)-hopeaphenol (6) showed potent activity, but less than that of doxorubicin.