[en] Complete text of publication follows. Kinetics of photodecomposition of three model dyes dissolved in isopropanol-water mixture has been determined after exposure to UV radiation in the range from 360 through 400 nm and from 220 through 400 nm, respectively. It has been disclosed earlier that photodecomposition of the dissolved dyes was decelerated initially by the presence of the dissolved oxygen in the system. The presence of a radical initiator, AIBN was indispensable for arriving at the decomposition of the irradiated dye solution in the range from 360 through 400 nm. The equation of W_i^D = [O₂]/τ^D was used for the calculation of radical initiating rate of the irradiated dye molecule on the isopropanol (W_i^D (mol/l x s)), where [O₂] (mol/l) is the dissolved oxygen concentration in the system and τ^D (s) is duration of the induction period of the photodestruction of the dissolved dye. The equation is valid only for photodecomposition which are not chain reaction. The photodegradation of dissolved dyes was also other then chain reaction, consequently the above equation could be applied in the study too. The average radical initiating rate of the dyes applied in this study was in the order of magnitude equal to that of AIBN. The number of cycles between the first radical formation and the last regeneration of the dye molecule could be calculated in bath systems (in the presence and absence of oxygen, respectively): K = W_i^D/W_D, where K is the number of cycles, W_D (mol/l x s) is the initial rate of the decomposition of the dissolved dyed. The number of cycles in the oxygen containing systems significantly exceeded those obtained in the oxygen systems because W_D was markedly higher in the latter system than in the former one