Phellinus linteus and igniarius (L.) Quel. have been used in traditional Asian medicine for over two centuries against a variety of diseases. Polysaccharides from their fruiting bodies show strong immunomodulatory activity. In this study we characterized the structure and composition of polysaccharides from Phellinus linteus and Phellinus igniarius by HPLC, GC-MS and NMR (1-H, 13-C, COSY, NOESY and TOCSY). The polysaccharides from P. linteus and P. igniarius mainly contained glucose with minor proportions of mannose, galactose, xylose, arabinose and rhamnose. Methylation analyses showed that the glycosidic linkages were mostly 1 → 3, 1 → 6 or 1 → 3,6. The two-dimensional COSY, NOESY and TOCSY confirmed that these polysaccharides have a main chain of →3)-β-d-Glcp-(1→ with →6)-β-d-Glcp-(1→ side chain. In vitro assays by RT-PCR and ELISA showed that (1 → 3; 1 → 6)-β-d-polysaccharides from P. linteus and P. igniarius decreased TNF-α in RAW 264.7 cells, suggesting an immuno-suppressive activity. Furthermore, these polysaccharides stimulated a high IL-10 response and induced strong suppression of transcription of IL-6. The results suggest that polysaccharides from P. linteus and P. igniarius could possibly find applications in restoring the IL-6/IL-10 balance, the disturbance of which is thought to be related to chronic inflammatory disease, obesity, diabetes type 2, and to mania and depression.