Transporters such as P-glycoprotein (MDR1), multidrug resistance protein 1 (MRP1), lung resistance-related protein (LRP) and breast cancer resistance protein (BCRP) are associated with multidrug resistance in various carcinoma cell lines. The expression of these molecules has been also characterized in human normal tissues. However, the expression of these molecules in oocyte is still unclear. In order to obtain more insight into the physiological role of these transporters, their expression in porcine oocyte were examined by reverse transcriptase-polymerase chain reaction. MDR1, MRP1 and LRP genes, but not BCRP gene were found to be expressed in porcine oocyte. After the subcloning and sequence analysis of MDR1, MRP1 and LRP genes, the high homology of these transporters were observed between porcine and human gene. These findings suggest that MDR1, MRP1 and LRP play an important physiological role(s) in an oocyte.