Chemical investigation of the EtOH extract of the twigs of Calophyllum inophyllum collected in Hainan Province of China resulted in the isolation of two new prenylated xanthones, caloxanthone O (1) and caloxanthone P (2). Their structures were elucidated by a study of their physical and spectral data. Compound 1 exhibited cytotoxicity against human gastric cancer cell line (SGC-7901),with an IC50 value of 22.4 microg mL-1.