Kinetics of Radachlorin photosensitizer fluorescence in aqueous solution excited by CW laser radiation at 405 nm has been studied. Interpretation of the experimental results was based on numerical solution of a set of rate equations. Rate constants of possible bleaching mechanisms were determined and an electron transfer reaction between triplet state photosensitizer and oxygen molecules was found to be the main bleaching mechanism. The fluorescence intensity was almost independent of the oxygen concentration indicating that the triplet state degradation occurs mainly in collisions with oxygen molecules. The results obtained can be utilized for providing optimal conditions for singlet oxygen generation. (C) 2016 Elsevier B.V. All rights reserved.