A B S T R A C T Background: One of the active ingredients purified from Shiitake edible mushrooms is lentinan, the backbone of β-(1, 3)-glucan with β-(1, 6) branches. It has been approved in Japan as a biological response modifier for the treatment of gastric cancer. Objective: This review discusses the purification and characterization of lentinan's potential mechanism of action, clinical application of lentinan, and future potential uses because a deeper comprehension of its biological activities should allow to use lentinan more effectively in the treatment of gastric cancer. Method: Lentinan is a high molecular weight β-glucan was purified from the fruiting body of Lentinula edodes RSR by ethanol precipitation fractionation and purified by gel chromotography column (2.5 cm X 7.8 cm length). Results: The absorbance of the separated 40 fractions were recorded at the wavelength at 280 nm, as well as the concentration of the lentinan was determent by ELISA .The results characterization of purified lentinan was proved that the glucan in Lentinan was composed of (1-3)-βD-linkages. Conclusion: The aim of the present study to purified and characterized of lentinan from new Iraqi strain for using it as an alternative compound to medicines and chemical compounds.