Aim:　To　investigate　whether　Rhizoma　curcumae　could　induce　pregnane　X　receptor(PXR)-mediated　transcriptional　expression　of　CYP3A4　and　study　the　modulatory　effects　on　the　enzyme　activity　and　mRNA　expression　of　CYP3A　in　the　rat　liver.　Methods:　Transient　cotransfection　reporter　gene　assays　were　performed　in　HepG2　cells;　the　rat　liver　microsomal　cytochrome　P450　and　CYP3A　isoenzyme-erythromycin　N-demethylase(ERD)　activities　were　determined　by　UV　chromatography;　the　mRNA　expression　level　of　CYP3A　was　detected　by　reverse　transcriptase-polymerase　chain　reaction　(RT-PCR).　Results:　In　vitro　investigation　showed　Rhizoma　curcumae　and　its　four　selected　constituents　could　induce　the　CYP3A4　transcriptional　expression　by　activating　PXR.　In　vivo　investigation　showed　the　CYP450　content　of　liver　microsomes　and　enzyme　activity　of　CYP3A　were　markedly　increased　and　induced　by　Rhizoma　curcumae　extract;　at　the　mRNA　level,　the　expression　of　CYP3A1　and　CYP3A2　gene　were　markedly　induced　by　Rhizoma　curcumae　extract.　Conclusions:　Rhizoma　curcumae　and　its　four　selected　constituents　could　induce　the　expression　of　the　CYP3A4　gene　transcriptional　expression　through　activating　PXR;　Rhizoma　curcumae　extract　could　increase　and　induce　the　enzyme　activity　and　mRNA　expression　of　CYP3A.