In order to investigate the immunostimulating effect of mycelia extract of Phellinus linteus (PLM) on human monocyte THP-1 and rat peritoneal macrophage cell, we examined measuring cytokine secretion (IL-6 and TNF-${alpha}$). The production of IL-6 and TNF-a in human monocyte THP-1 was slight increased dose-dependently when the cells were challenged with PLM for 72 hrs. It was also observed that the treatment of PLM with LPS augmented the production of IL-6 and TNF-a in human monocyte THP-1. It was also observed that the treatment of PLM with LPS augmented the production of IL-6 and TNF-${alpha}$ in human monocyte THP-1. The production of IL-6 and TNF-${alpha}$ in rat peritoneal macrophage was significantly enhanced when the cells were treated PLM with LPS for 72 hrs. Moreover, the proliferation rate of rat spleen cells was increased in a dose dependent manner as the cells were treated with PLM and Concanavalin A.