Interleukin-12, a heterodimeric cytokine comprising p40 and p35 subunits, plays an essential role in the regulating the differentiation of Th cells, which establish and maximize the capabilities of the immune system. The aim of present study is to screen the effect of 21 ginsenosides from steamed ginseng-leaves and flowers on IL-12 production in bone marrow-derived dendritic cells induced by lipopolysaccharide. Noticeably, ginsenoside $Rg_6$ (12) and ginsenoside $F_4$ (13) exhibited particularly inhibitory effect on LPS-induced IL-12 production with the inhibition values of 80 and 82%; and ginsenoside $ST_1$ (4), ginsenoside $SL_2$ (8), ginsenoside $SL_3$ (9), ginsenoside $Rh_3$ (14), ginsenoside $Rk_2$ (15), and ginsenoside $Rs_4$ (18) showed moderate effects with inhibition rates of 63, 65, 67, 68, 71, 73, and 67%, respectively. These results warrant further studies concerning potential of saponin extracts of steamed ginseng-leaves and flowers for medicinal uses.