The high solubility, polarity and recalcitrant nature of naphthalene sulphonates render their treatment by conventional physicochemical and biological methods a rather difficult task. The present study aimed at investigating the treatability of a commercially important naphthalene sulphonate, e.g. H-acid, using H2O2/UV-C and Fe2+/H2O2/UV-C photochemical oxidation processes. The H2O2/UV-C process was capable of 100% H-acid, 48% COD and 27% TOC removals 180 min under the experimental conditions of 468 mg/l initial COD, 60 mM initial H2O2 concentration and an initial pH of 5.9-6.0. A steady increase in the average oxidation state throughout the photochemical reaction revealed that more oxidized organic intermediates were formed during H2O2/UV-C treatment of H-acid. The effect of initial H2O2 concentration on H2O2/ UV-C treatment efficiency was examined by conducting experiments at varying initial H2O2 concentrations up to 200 mM. An initial H2O2 concentration of 150 mM appeared to be the optimum where the highest rate constants and removal effi ciencies were obtained in terms of H-acid, COD and TOC abatements. Fe2+/H2O2/UV-C oxidation of H-acid was appreciably faster than the H2O2/UV-C process causing a significant increase in the organic carbon (COD, TOC) removal efficiency when Fe2+ was applied as the photocatalyst. For the Photo-Fenton process carried out in the presence of 1.0 mM Fe2+, 96% H-acid removal was achieved in only 10 min, while 92% COD and 85% TOC abatements were attained after 60 min photochemical treatment (experimental conditions: initial COD = 463 mg/l; initial H2O2 = 30 mM and initial pH = 3.0 +/- 0.1). Photo-Fenton degradation kinetics established on the basis of initial H-acid, COD and TOC abatement rates as well as treatment effi ciencies followed the decreasing order of Fe2+/H2O2/ UV-C (1.0 mM Fe2+) > Fe2+/H2O2/UV-C (0.2 mM Fe2+) > H2O2/UV-C.