In this study, we investigated the in vitro anti-obesity, anti-cancer activity and single oral dose toxicity of Inonotus xeranticus extracted by methanol (INXM) or ethyl acetate (INXE). In order to investigate anti-obestity effect of Inonotus xeranticus extracts, the 3T3-L1 cells were treated with these extracts at various concentrations(1, 10, 100 and 300 ㎍/㎖). It was observed that 3T3-L1 cells treated with 100 ㎍/㎖ of Inonotus obliquus ethyl acetate extract (INOE), INXM and INXE, in the absence of differentiation cocktail (0.5 mM isobutylmethylxanthine (IBMX) 1 μM dexamethasone, 1 ㎍/㎖ insulin), differentiated at a rate of 78.5, 80.9, and 76.4% respectively. Differentiation rates of 86.6% and 83.4% were observed in 3T3-L1 cells which were treated with differentiation cocktail at 100 ㎍/㎖ of INXM and INXE, respectively. The anti-cancer effect of Inonotus xeranticus extracts was investigated using a method of sulforhodamine B in sarcoma 180 cell line. The cells were treated with these extracts (1, 10, 100 and 300 ㎍/㎖) for 48 hours. The growth of cells which were treated with 300 ㎍/㎖ of INXM was inhibited by 80.1%. The growth of sarcoma 180 cells which were treated with 100 and 300 ㎍/㎖ of INXE was inhibited by 74.7% and 64.5%, respectively. In single oral dose toxicity study, no differences were observed between control and treated groups in clinical signs, body weight gains, and feed and water consumptions. The results indicated that Inonotus xeranticus extracts did not show any toxic effects at 2,000 ㎎/㎏ in mice, and the LD?? of these extracts was found to be higher than 2,000 ㎎/㎏ in this experiment. From the above results, Inonotus xeranticus methanol and ethyl acetate extracts might have useful clinical applications in the management of cancer and obesity and may also be useful as a medicinal food.