This book describes the structures of Metallothionein (MT) family members and the cellular functions of MT-1, MT-2 and MT-4 isoforms, as well as provides insights into divergent biological roles of MT-3. The authors explain the involvement of MT molecules in various processes related to carcinogenesis, including an organ-specific presentation of current data concerning their potential impact on the progression of various tumors and the regulatory role of MT family members in the function of the immune system.