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The structure of CH4 monolayer physisorbed on a Ag(111) surface was observed by LEED. The LEED patterns were recorded with suppressed electron current using a cooled CCD camera in order to minimize theelectron stimulated desorption of adsorbed CH4. The LEED pattern indicated that the lattice of CH4 molecules forms hexagonal structure in rotationally ordered incommensurate state. Under specific equilibrium condition, intermediate state with the coverage less than unity was found to exist. 1.