Preparation of amorphous phase of a photochromic dye, cis-1,2-dicyano-1,2- bis(2,4,5-trimethyl- 3-thienyl) ethene, has been investigated and its photochromic properties have been studied. This photochromic dye shows clear photochromism in the amorphous solid state accompanying reversible changes in absorption spectrum, refractive index, and dielectric properties. Clear optical pattern formation has been achieved on the amorphous dye layer.