Spectral properties and photochromic behavior of a series of novel 1',3',3'-trimethyl-1,2-tetramethylenespiro-[7H-furo(3,2-f)-(2H-1)-benzop yran-7,2'-indolines] 1-4 have been studied. The mechanism of the photoinitiated ring-opening reaction involves the formation of an acoplanar cis-cisoid intermediate, the lifetime of which in the case of 6-(tert-butyl) derivative 4 is long enough to observe its absorption and fluorescence spectra under conditions of continuous irradiation. The occurrence of the intermediate on the reaction paths of the thermal and photochemical ring-opening processes has been also shown by the DFT and CIS calculations. The TD-B3LYP/6-31G**//HF/6-31G** calculated spectrum of the intermediate well matches that observed experimentally. For spiropyran 3 with a 6-NO2 group, kinetic and activation parameters of the photoinitiated coloration and dark bleaching reactions have been determined.