ABSTRACT The marine sponge Xestospongia sp. was collected along seashore area of Lan Yu in Taiwan. Fractionation of the MeOH/CHCl3 extract by using silica gel colum chromatography yielded eight polycycle quinones and hydroquinones ,namely halenaquinone (1)¡B halenaquinol(2)¡B14-methoxyxestoquinone (3)¡B15-methoxyxeatoquinone (4)¡B xestoquinone (5)¡B15-chloro-hydroxestoquinone (6) ¡Badociaquinone A (7)¡B adociaqunone B (8) . The structures of these compounds were idenified by UV¡BIR¡BMS¡B 1D and 2D NMR . Biological screening revealed that compounds 7 and 8 possessed in vitro cytotoxicities against two tumor cell lines (KB 16, HEPA-3B). The ED50 value of compound 7 showed cytotoxicities against KB 16 and HEPA-3B tumor cell lines were 0.26 £gg/mL and < 0.1 £gg/mL, respectively. The ED50 value of compound 8 were < 0.1 £gg/mL and 1.8 £gg/mL .