Aim: To investigate the effect of water soluble-ethanol precipitation fraction (AC-1) and alkaline extraction-isoelectric precipitation fraction (AC-2) from Antrodia camphorata (Polyporaceae, Aphyllophorales) on lipopolysaccharide (LPS)-in-duced gene activation in mouse macrophages. Methods: The AC-1 and AC-2fractions were prepared, and their effects on LPS-induced gene expression were monitored by Weste blotting and RT-PCR. Results: Our results indicated thatAC-2, but not AC-1 dose-dependently (50--200 mg/L) inhibited LPS-induced nitric oxide production as well as the protein and the mRNA expression of the inducible nitric oxide synthase (iNOS) gene. Neither AC-1 nor AC-2 inhibited LPS-inducedcyclooxygenase-2 gene expression. Using the cytokine array assay, it showed that AC-2 also had the ability to inhibit LPS-induced the protein expression of interleukin (IL)-6, IL-10, the monocyte chemoattractant protein (MCP)-5, and regulated upon activation, normal T-cell expressed, and presumably secreted (RANTES). Like iNOS, AC-2 inhibiting LPS-induced IL-6 and IL-10 secretion resulted from inhibiting their mRNA expression. Conclusion: It was suggested that alkaline extraction-isoelectric precipitated the polysaccharide fraction of A camphorata and had the ability to inhibit LPS-induced iNOS, IL-6, IL-10, MCP-5, and RANTES expression in mouse macrophages.