The mouse constitutive androstane receptor (mCAR), with the retinoid X receptor, binds to the retinoic acid response element to upregulate the expression of proteins that metabolize xenobiotics. TCPOBOP is an agonist for mCAR (EC50 = 20 nM) that is effective for the mouse receptor but not for human or rat CAR receptors. Through its effects on mCAR, TCPOBOP potently induces cytochrome P450 monooxygenases and multidrug resistance and xenobiotic efflux proteins. The action of TCPOBOP on mCAR-mediated gene expression can be repressed by retinoic acids.