Smectite-type clay particles dispersed in an aqueous subphase stabilize a monolayer of water-soluble alkylammonium cations at an air-water interface. When a chloroform solution of the alkylammonium salt is spread onto the clay dispersion, the ammonium cations are adsorbed on the clay particles electrostatically at the interface to form a floating hybrid monolayer. Atomic force microscopy (AFM) observation of the film confirms hybridization of the ammonium cations with the clay particles.