A new type of photocatalytic reactor, the spinning disc reactor (SDR), was used to degrade aqueous solutions of 4-chlorophenol and salicylic acid. The eciency of the photocatalytic process depends on the type of UV source used. Lamps supplying shorter wavelength UV radiation are more ecient than those whose emissions lay mainly in the near UV region. The method used to coat the disc of the SDR does not meet its operational requirements. The characteristics of the turbulent liquid ®lms produced in the SDR reduce the in¯uence of mass transfer over the overall photocatalytic process. Ó 2000 Elsevier Science Ltd. All rights reserved.