The absorption of phenothiazine dyes, thionine (TH+), azure-A(+) (Az-A(+)), and methylene blue (MB(+)) into Nafion film was studied, and the standard free energy of hydrophobic interaction (Delta G degrees(h)) was calculated for the dyes. Electrochemical and spectroelectrochemical studies of these dyes in Nafion film were also carried out to understand the electrochemical behavior and their interaction with the Nafion film. TH+ and Az-A(+) showed different electrochemical behavior in Nafion film when compared to aqueous solution. The hydrophobicity of reduced dye molecules was found to influence the electrochemical properties of the dye molecules in Nafion film. The spectroelectrochemical studies of dyes in Nafion film showed complete reduction of monomer, dimer, and protonated dye molecules. Upon the oxidation of reduced dye molecules in Nafion film, dimer and protonated dyes were formed.