An imidazole-containing amphiphile, 4,5-imidazoledicarboxylic acid monostearyl ester (1), was synthesized via esterification of 4,5-imidazoledicarboxylic acid with stearyl alcohol. Monolayer properties of 1 at the air-water interface were studied by measuring surface pressure-area isotherms. The molecular surface area of the monolayers were expanded at acidic or basic subphases compared with that on pure water subphase. The monolayers on subphases containing metal ions showed increased stability against surface pressure and rather expanded molecular area than on pure water subphase. The monolayers were poorly transferred on quartz and calcium fluoride plates as Z type. UV-visible and FT-IR spectra were used to characterize the LB film.