Metallothioneins (MTs) are low molecular weight, cysteine-rich, and heavy metal binding proteins, which could be induced with heavy metals such as Cd, Hg, Zn and Cu in liver, kidney, and in cultured cells. By using ion exchange chromatography on DE-52, MT was purified from the serum of carp induced with cadmium in order to produce antibody against MT. Polyclonal antibody produced against purified carp MT reacted well with MT in the serum of carp induced with cadmium, whereas control serum did not. This may indicate that the polyclonal antibody against the carp MT could be used for the preparation of biosensors to detect MT in fishes like carp.