Langmuir-Blodgett (LB) films of dilithium octacyanophthalocyanine [Li2Pc(CN)(8)] were first prepared, and their electrochemical reduction/reoxidation behaviors were studied in detail. An overwhelming majority of the Li2Pc(CN)(8) molecules in the LB film were stacked in a face-to-face aggregated state and stood obliquely with an edge-on configuration on the substrate surface. Two overlapping redox waves were observed in the voltammogram of the LB film in I mol dm(-3) HCl solution. Their relative intensity was found to be largely dependent on the molecular aggregation state in the film. On the basis of spectroscopic and electrochemical analyses, the first and second reduction waves upon cathodic potential scanning were principally assigned to the aggregated and monomeric Li2Pc(CN)(8) molecules, respectively, in the solid film structure. In comparison with the corresponding solvent-cast film, charge transfer within the LB film and/or through the electrode interface was facilitated, and the LE film showed excellent dynamic character in the redox process.