Polycyclic aromatic hydrocarbons (PAH's) are a class of persistent organic pollutants of special concern since they are carcinogenic and mutagenic. In this paper, the design of a continuously stirred tank reactor is reported for the photodegradation of the simplest and most water-soluble PAH, naphthalene, in water using TiO2 (in the crystalline form of anatase), supported on glass Raschig rings as catalyst, with oxygen as electron acceptor. A first order kinetic rate constant has been calculated for this photodegradation. The irradiated solution after the reaction has been analysed and only traces of 1-naphthol, 1,4-naphthalenedione and phthalates have been found as intermediate products of the photodegradation. (c) 2005 Elsevier B.V. All rights reserved.