The characteristics of the transient species formed in the reaction of Reactive Red-120 dye (RR-120) with selective one electron oxidants viz. N₃^·, Cl₂^·-  and selective one electron reductants viz. (CH₃)₂C^·OH and CO₂^·- radicals in aqueous solution were studied by pulse radiolysis technique. The rate constants for the oxidation reaction of RR-120 with N₃^·, Cl₂^·- were determined as 1.1 x 10⁹ and 1.0 x 10⁸ dm³mol^-1s^-1, while that of reduction reaction with (CH₃^·)₂C^·OH, and CO₂^·- radicals were obtained as 1.8 x 10⁹, and 1.4 x10⁸dm³mol^-1s^-1, respectively. Lower value of the rate constant for the reaction of CO₂^·- radicals with RR-120 is attributed due to the coulombic repulsion between the negative charges on RR-120 and CO₂^·- radicals at pH 6.8. Steady state gamma radiolysis of aqueous solution of RR-120 dye was also investigated under the same oxidising and reducing conditions as performed in the pulse radiolysis experiment. Since the N₃^·  radicals are more selective one electron oxidising agent than hydroxyl radicals (OH^·), thus more efficient decoloration was observed in the reaction of RR-120 with N3 radicals as compared to the same with OH^·  radicals. Decoloration efficiency was found identical for the reaction of RR-120 with (CH₃)₂C^×OH, CO₂^- radicals and hydrated electrons (e_aq^-). Transients produced in the reaction of RR-120 with e_aq^- may react with tert-butanol radicals and thus differ from the decay traces of the transient species produced in the reaction of RR-120 with (CH₃)₂C^×OH radicals. Therefore, G(-dye) was observed higher for the reaction of RR-120 with e_aq- than with (CH₃)₂C^×OH radicals.