The photocatalytic conversion of two beta-blockers, namely atenolol and propranolol in aqueous TiO2 suspensions was investigated. Irradiation was provided by a solar simulator equipped with 1 kW Xe-OP lamp, while emphasis was given on the effect of catalyst type and loading (50-3000 mg/L), substrate concentration (5-30 mg/L), initial solution pH (3-10), and the addition of H2O2 (0.07-1.4 mM) and oxygen on degradation in two matrices (i.e. pure water and treated municipal effluent). Of the various catalysts tested, Degussa P25 was highly active yielding up to about 80% conversion after 120 min of reaction. In general, conversion was favored at lower substrate concentrations, near-neutral pH values and in the absence of other organics (i.e. in pure water), while the addition of H2O2 did not accelerate kinetics which seem to follow the Langmuir-Hinshelwood model. Toxicity to D. magna was evaluated prior to and after photo. catalytic treatment. Toxicity increased during the early stages of the reaction and then progressively decreased upon the elimination of the substrate and its reaction intermediates, with propranolol being more toxic than atenolol. (C) 2011 Elsevier Ltd. All rights reserved.