We report the use of redox-active surfactants Fc(CH2N+(CH3)(3) . Br-, where Fc = ferrocene = [eta(5)-C5H5]Fe[eta(5)-C5H5] and n = 8, 11, or 15, in a study of principles far active control of interfacial properties of aqueous solutions. By comparing the surface activity of Fc(CH2N+(CH3)(3) with that of HO(CH2N+(CH3)(3) and CH3(CH2N+(CH3)(3), we demonstrate that Fc(CH2N+(CH3)(3) behave as unsymmetrical bolaform surfactants with one ionic "head" group (N+(CH3)(3)) and one nonionic "head" group (Fc), whereas ferrocenyl surfactants, when oxidized to Fc(+)(CH2N+(CH3)(3), have properties of symmetrical bolaform surfactants such as N+(CH3)(3)(CH2N+(CH3)(3). Oxidation of Fc(CH2N+(CH3)(3) to Fc(+)(CH2N+(CH3)(3) leads to changes in interfacial properties through three mechanisms, at least. First, near their critical micellar concentrations (cmc’s), oxidation caused desorption of monolayers of Fc(CH2N+(CH3)(3) and Fc(CH2N+(CH3)(3) from the surfaces of their aqueous solutions, thereby recovering the surface tension of the aqueous electrolyte. Sire measured changes in surface tension as large as 23 mN/m. Second, at concentrations greater than the cmc, oxidation of Fc(CH2N+(CH3)(3) caused little, if any, change in the excess surface concentration of surfactant. The accompanying increase in the density of charge within the monolayer did, however, cause a decrease in surface tension of 6 mN/m. Third, oxidation of Fc(CH2N+(CH3)(3) caused its monolayers at the surface of water to change from condensed states to expanded ones at constant surface pressure. We infer the phase transition within the monolayer to be driven by changes in conformation that accompany the transfer of ferrocene, upon oxidation, from the outer region (side in contact with air) of the condensed monolayer into contact with the aqueous subphase.