Mast cells and basophils perform important functions as pivotal effector cells in IgE-mediated allergic reactions. KU812F cells, a human basophilic cell line isolated originally from chronic myelocytic leukemia, express a high affinity receptor of IgE, $Fc{varepsilon}RI$. Kaempferol was extracted and isolated from a methanolic extract of flavonoid-rich Nelumbo nucifera stamens. In the present study, the inhibitory effects of kaempferol on $Fc{varepsilon}RI$ expression in human basophilic KU812F cells was examined. Flow cytometric analysis revealed that $Fc{varepsilon}RI$ expression on the cell surface was suppressed in a concentration-dependent manner when the cells were cultured with kaempferol. Moreover, RT-PCR analysis showed that the mRNA levels for $Fc{varepsilon}RI$ ${alpha}-;and;{gamma}$-chains were reduced as the result of kaempferol treatment in a concentration-dependent manner. Kaempferol showed its suppressive effects on intracellular $Ca^{2+}$ concentration and histamine release from anti-$Fc{varepsilon}RI$ ${alpha}$-chain antibody-stimulated cells in a concentration-dependent manner. These observations indicate that kaempferol may exert antiallergic effect via down regulation of $Fc{varepsilon}RI$ expression and degranulation.