A rigid macrocyclic oligomer (RCO), cyclic poly(aryl ether ketone), was synthesized and used to produce Langmuir-Blodgett (LB) films. The isotherm of surface pressure versus surface area showed that the RCO molecules form a stable monolayer on the water subphase with an area per molecule of about 1.7 nm(2). The structure of the LB film was confirmed by means of atomic force microscope, and two-dimensionally ordered cavities of nanometer scale were observed in the LB film.