In the previous paper (Kim et al., Glycoconjugate Journal 16, 247-252, 1999), heteropolysaccharides from Korean medicinal plant, Phellodendri cortex (Hwangbek) showed a poten B-Iymphocyte-stimulating activity in a system using polyclonal antibody forming cells in C57BL/6XC3H mice at dosages of 2-10 mg. In a series of biolgical active polysaccharides from natural medicinal plants, the polysaccharide fractions were isolated and purified from Phellodendron chinese SCHNEID, and antitumor activities were examined at dosages of 2, 5 and 10 mg/100 g. F-7 and F-8 showed the highest tumor inhibitory activities (inhibition ratio 96.4 and 98.2% in 2 mg/100 g), and in dose of 5 mg/100 g, the inhibitory ratios were 95.3 and 97.5%, respectively. Furthermore, 10 mg/100 g of intraperitoneal (i.p.) injection gave 97.3 and 98.7% of inhibition. In oral administration, the inhibitory activities were not markedly observed, indicating that the polysaccharides are directly acting to immune system. When the effects on TS and TK activities were determined, TS activities in the F-2 and F-7-treated mice were markedly suppressed to 73.7% and 79.5% of that in the control (p<0.01), while there was little difference in TK activity with a slight decrease in F-2 only. However, in i.p. injection, TS activities in the F-2, F-5, F-7 and F-8-treated mice were markedly suppressed to 83% to 85% of that in the control (p<0.01). Furthermore, there was also significant differences in TK activities in F-2, F-5, F-7 and F-8-treated mice (p<0.05). Therefore, polysaccharide fraction F-8 was further purified to active fractions of F-9 and F-11 by gel permeation chromatography using TSK Gel HW50S. The purified polysaccharides of F-9 and F-11 were composed of GlcNAc (47.3%), Gal (24.7%) and Man (28.0%). These results clearly indicated that the i.p. injection is much effective to suppress tumor growth than oral administration.