Transporters in kidney are critical in detoxification and elimination of xenobiotics from systemic circulation, and thus are major determinants of drug response and sensitivity. Transporters in the renal epithelium control the exposure of renal cells to nephrotoxic drugs and environmental toxins and thus determine xenobiotic-induced nephrotoxicity. Organic anion transporters (OATs) and organic cation transporters (OCTs) are two major classes of secretory transporters in the mammalian kidney. Among the uptake transporters, OAT1, OAT3, or OCT2 appear to be particularly important in the renal basolateral membrane to transport a large variety of endogenous and therapeutic compounds.