Abstract 1,2-Bis(2,4-dimethy-3-thienyl)perfluorocyclopentene was found to undergo a reversible photochromic reaction in a single crystalline phase with rotation of the thiophene rings. Both the open-ring colorless and the photogenerated red isomers were thermally stable even at 100 °C. Coloration/decoloration cycles could be repeated more than 100 times without destruction of the crystal shape. Regular alignment of the photogenerated colored isomers in the crystal was evidenced by the absorption measurement under linearly polarized light.