The decolourization of the azo dye Acid Black 24 was investigated using a homogeneous advanced oxidation process which comprised irradiating aqueous solutions of the dye with UV light at a wavelength of 254 nm in the presence of either hydrogen peroxide, sodium persulphate or sodium periodate at a pH of 6.3. In all three cases, increasing the concentration of oxidant resulted in an enhancement in the rate of dye decolourization. First-order kinetics adequately described the disappearance of the dye. Reaction rate orders with respect to the oxidant species were 0.23, 1.17 and 0.90 for, respectively, peroxide, persulphate and periodate. The extent of dye mineralization was monitored by TOC measurements which showed that the use of periodate resulted in a lower final TOC than was obtained with either peroxide or persulphate.