Self-assemblies of n-hexadecane and n-hexatricontane on the Au(1 1 1) surfaces in their neat liquid or solution have been studied by using scanning tunneling microscopy (STM). Ordered monolayers are observed on the reconstructed Au(1 1 1) surfaces, while no overlayer could be observed on the unreconstructed surface at room temperature. The reconstructed surface is found to be perfect for the n-alkanes to self-assemble on it, because the alkane monolayer geometrically matches well to the reconstructed surface. The reconstruction stabilizes the self-assembled monolayer on the Au(1 1 1) surface, which facilitates the observation of STM.