We demonstrate that paclitaxel, an antitumor agent derived from yew tree, inhibits LPS- and $IFN-{gamma}$-induced NF-kB/Rel activation in RAW 264.7 cells. Previously, paclitaxel ($>10{mu}M$) has been known to induce iNOS gene expression in macrophages. However, in the previous report we described that the pretreatment of macrophages with low concentration of paclitaxel ($0.1{mu}M$) for 8 h inhibited LPS-induced iNOS gene expression. Pretreatment of RAW 264.7 cells with paclitaxel significantly inhibited NF-kB/Rel transcriptional activation. Electrophoretic mobility shift assay further confirmed that pretreatment of macrophages with paclitaxel inhibited NF-kB/Rel DNA binding. Taxotere, a semisynthetic analog of paclitaxel, also inhibited LPS- and $IFN-{gamma}$-induced iNOS gene expression. Collectively, these series of experiments indicate that paclitaxel inhibits iNOS gene expression by blocking NF-kB/Rel activation.