The issue dealt with in this Letter is the study of the optical fatigue of poly-1,2-bis(2-methylthien-3-yl)perfluorocyclopentene (1) as prototype of backbone photochromic polymers recently proposed as materials for the development of new optical devices in photonics and optical imaging. An instrument has been built and measurements have been carried out, thus showing that a film cast from a chloroform solution of the photochromic compound (I) + polymethylmethacrylate reaches the limits set by technology as acceptable (20% decrease of the absorbance with the respect to the absorbance of the stationary state) at 3400 cycles. (C) 2004 Elsevier B.V. All rights reserved.