Abstract: AIM: To study the effects of icariin and its metabolites (baohuoside I, icaritin) on the production of proinflammatory cytokines by THP-1 cells. METHODS: Radioimmunoassay (RIA) was used to quantitate human IL-1α, IL-6, IL-8 and TNFα. RESULTS: Icariin and its metabolites were shown to stimulate production of IL-6 and inhibit production of IL-8 and TNFα in the presence of LPS and PMA. In the absence of LPS and PMA these metabolites stimulated IL-8 production, but suppressed IL-6 production. Whether LPS and PMA were used or not, icariin and its metabolites have significant inhibitory effect on the production of IL-1α. CONCLUSION: These findings suggest that icariin and its metabolites, baohuoside I and icaritin, have modulatory effect on the production of cytokines.