Detailed conditions of two novel methods; “spreading method” and “adsorption method” available for preparation of the monolayer assemblies (LB films) of cyanine dyes without long alkyl chains have been examined.Õuinocyanine and thiacarbocyanine dyes capable of J-aggregate formation in aqueous solutions were incorporated into arachidic acid monolayers in the form of the J-aggregate. Importance of electrostatic interaction between negative charge at the carboxyl group of arachidic acid and positive charge at the chromophore was disclosed through careful examination of the effects of pH change and addition of Cd²⁺ in the water subphase, as well as the kind of matrix molecules on the J-aggregation. LB films prepared by us are promising as a model system to study physicochemical properties of the J-aggregate because of their stability for at least several days in air at room temperature.