A soluble fraction of particulate glucan was prepared and evaluated for its anti-tumor and anti-bacterial activity. Thin-layer chromatographic analysis indicated that the soluble preparation was composed of a variety of polyglucoses. Intravenous administration of soluble or particulate glucan resulted in significant reductions in the growth of a syngeneic anaplastic mammary carcinoma and melanoma B16. Survival data demonstrated that intravenous administration of soluble or particulate glucan prolonged survival of A/J and C57BL/6J mice with subcutaneous tumor implants. As regards to bacterial infections, soluble and particulate glucan decreased renal necrosis in S. aureus challenged mice as compared to control mice. Although the exact nature of the active soluble fraction(s) of glucan remains to be delineated, these studies demonstrate that a soluble glucan preparation exhibits significant anti-tumor and anti-staphylococcal activity. The active soluble fraction of particulate glucan may be preferable to particulate glucan in view of the inherent ease of parenteral administration.