Fucoidan, a sulfated polysaccharide with several biological activities, is usually isolated from marine seaweeds or from echinoderms. Here, we report on the anti-tumour activity of fucoidan isolated from the aquatic plant Utricularia aurea Lour (Lentibulariaceae). A crude extract (CE) prepared by incubating U.aurea with hot water at 95oC for 12 hr was partially purified by Sephadex G-50, eluting with a 50mM sodium acetate buffer, at pH 5.0, containing 0.5M NaCl. Partially purified fucoidan (PPF) had a 3- fold increase in fucose content when compared with the CE and a molecular weig t of 11.6 kDa as determined by Sephadex G-200. Chemical analysis showed that CE consisted of 62.5% glucuronic acid, 5.0% fucose, 1.7% sulfate and 12.0% proteins while PPF consisted of 65.0% glucuronic acid, 15.3% fucose, 2.1 % sulfate and 8.3% proteins.The anti-tumour activity of the CE and PPF was determined by the MTT test. The CE at 125 μg/mL fucoidan and PPF at 250 μg/mL inhibited the growth of KB cells (a nasopharynx tumour cell line), but did not inhibit that of normal fibroblast cells. The inhibition was postulated to occur via apoptosis as significantlymore apoptotic cells were found after treatment than in the untreated KB cells (P<0.05) by the TUNNEL (TdT-mediated dUTP Nick-End Labelling) assay.