A new prenylated xanthone (1), named caloxanthone N, together with two known constituents, gerontoxanthone C (2) and 2-hydroxyxanthone (3), was isolated from the ethanolic extract of the twigs of Calophyllum inophyllum. Their structures were completely elucidated using a combination of 1D, 2D NMR techniques (COSY, HMQC, HMBC, and ROESY) and HR-ESI-MS analyses. Compounds 1 and 2 exhibited cytotoxicity against chronic myelogenous leukemia cell line (K562) with IC50 values of 7.2 and 6.3 microg ml(- 1), respectively.