This study evaluates the effect of mushroom beta-glucans (MBGS) derived from solid culture of Ganoderma lucidum on tumor inhibition by examining size of the primary tumor and rate of metastasis in Lewis lung carcinoma (LLC) bearing mice (C57BL/6), given oral administration of MBGS with radiation therapy. A previous result showed that MBGS enhances NK cell-mediated cytotoxicity in mice without LLC bearing in advance. Furthermore, applications of MBGS in conjunction with radiation therapy were effective in controlling tumor growth, and rate of metastasis, life threatening, and can potentially serve as a protective factor for wounds and hair loss that resulted from the overgrowth of primary tumor in LLC bearing mice.