Using time-resolved techniques of 337 and 248 nm laser flashphotolysis, the photophysical and photochemical processes of riboflavin (RF, vitamin B2) were studied in detail in aqueous solution. The excited triplet state of riboflavin (3RF*) was produced with 337 nm laser, while under 248 nm irradiation, both 3RF* and hydrated electron () formed from photoionization could be detected. Photobiological implications have been inferred on the basis of reactivity of 3RF* including energy transfer, electron transfer and hydrogen abstraction. The RF·+ was gene- rated by oxidation of SO4·- radical with the aim of confirming the results of photolysis