A new gene which called multidrug resistant associated protein gene (MRP) was found in the study of the mechanism of multidrug resistance of cancer. The cognate gene is located on chromosome 16 at band P13∶3. Its mRNA encodes a member of the ATP-binding cassette transmemberance transporter superfa-mily with a mass of molecular 190 ku (p190). The MRP is mainly located on the plasma membrane and may play a role in the ATP dependent transport system. Further study indicates that apart from some kind of cancer cell lines, MRP overexpression was found in some blood malignancy, breast cancer, lung cancer and so on. The overexpression may be also related to the relapse of cancer.