Many components that are derived from medicinal or dietary plants possess potential chemopreventive properties. Curcumin, a yellow coloring agent from turmeric (Curcuma longa Linn, Zingiberaceae), possesses strong antimutagenic and anticarcinogenic activities. In this study, we have found that curcumin inhibits the 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced nuclear factor ${kappa}B$ (NF-${kappa}B$) activation by preventing the degradation of the inhibitory protein $I{kappa}B{alpha}$ and the subsequent translocation of the p65 subunit in cultured human promyelocytic leukemia (HL-60) cells. Alternatively, curcumin repressed the TPA-induced activation of NF-${kappa}B$ through direct interruption of the binding of NF-${kappa}B$ to its consensus DNA sequences. Likewise, the TPA-induced DNA binding of the activator protein-1 (AP-1) was inhibited by curcumin pretreatment.