Abstract: Transient absorption spectra in the photocolouration of 1-n-octyl-3,3-dimethylindolino-2,2'-spiro-5',6'-(2-bromo-4-nitro-benzo)-pyran (SPP1), 1-n-octyl-3,3-dimethyl-indolinn-2,2'-spiro-5',6'-(4-nitro-benzo)-pyran (SPP2), 1-n-octyl-3,3-dimethylindolino-2,2'-spiro-5', 6'-(2, 4-dinitro-benzo)-pyran (SPP3) and 1-n-octyl-3,3-dimethylindolino-2,2'-spiro-5', 6'-(2-chloro-4-nitro-benzo)-pyran (SPP4) in toluene and eyclohexane were investigated with nanosecond laser photolysis. Several certain intermediats and an aggregate were observed. The mechanism of the isomerization involves not lnly triplet process but also singlet process.