Highly ordered PcPS (phthalocyaninatopolysiloxane) thin films have been produced on a variety of substrates using Tangmuir-Blodgett thin-film deposition techniques, with coverages ranging from 1 to 100 molecular layers. Siloxane-polymerized cofacial phthalocyanines, with alkoxyhydrocarbon side chains on the individual Pc units, yield molecules capable of forming highly ordered, densely packed LB films, with individual polymeric-Pc chains ranging in size up to ca. 100 Pc monomer units each. These ultrathin films shows facile electron and ion transport during electrochemical and chemical oxidation and notable stability of the Pc cation radicals in the polymer chains in contact with both aqueous and nonaqueous media. Coulometric and spectroelectrochemical data suggest the oxidation of at least 80 --> 100% of the Pc rings at potentials up to ca. 1.0 V and the onset of formation of Pc dication species. There is a strong anion dependence for both the extent and rate of oxidation of the PcPS films in aqueous media. Anion incorporation can occur over a wide potential range from aqueous media, however, without the apparent low of film structure or stability.