Self-assembled-mono- and multilayer films have been formed via selective ionic interactions.(1) Two types of molecule have been used, straight chain mercaptoalkanoic acids and those containing chromophores : HS(CH2)(15)COOH and HS(CH2)(11)O-C6H4-SO2(CH2)(5)COOH. To better understand the formation process, XPS studies have been performed. Models are presented for various possible orientational structures, and evidence for a preferred orientation is given. The oxidation state of the copper ions within the films has been unambiguously determined.