Abstract: AIM: To investigate the chemical constituents from the seeds of Millettia pachycarpa. METHODS: The compounds were isolated and purified by repeated column chromatography. Their structures were elucidated on the basis of spectroscopic analyses, and their cytotoxic activities against human tumor cell lines (7860, A549, A2780, Hela, K562) and murine tumor cell lines (LL/2, B16) were evaluated by MTT assay. RESULTS: Four flavonoids were obtained and their structures were identified as 3-hydroxy-4-methoxylonchocarpin (1), 4-methoxylonchocarpin (2), isobavachromene (3), and dorspoinsettifolin (4). CONCLUSION: Compound 1 is a new prenylated chalcone, and compounds 2-4 were isolated from this genus for the first time. Compounds 1-4 selectively showed moderate inhibition against one or more of the tested cell lines.