A ligand exchange of trichloro-2,2'-dipyridylstearylamine ruthenium(III) (Ru(dps)Cl-3) monolayer was investigated at the air-water interface and in the LB film. The optical image of the monolayer was monitored by Brewster angle microscopy. When the monolayer was spread on alkaline subphase (pH 11), the surface pressure spontaneously increased up to 15 mN/m. The lambda (max) around 550 nm of UV-Vis absorption spectra of Ru(dps)Cl-3 in chloroform was shifted to around 670 mn in the LB film. The FT-IR spectra of the LB films also supported the two-dimensional ligand exchange of chloride to water or hydroxide ions.