Long-range-ordered, high-density gold (Au) nanodot arrays were prepared by vapor deposition using anodic porous alumina as a mask. The optical properties of such arrays were examined. The effects of highly ordered, high density arrangements of Au nanodots on the optical properties were elucidated by the dependences of the wavelength (lambda(max)) of the absorption maximal on the dot height and the refractive index of the solvent in which the An nanodot arrays were immersed.