Gas chromatography/mass spectroscopy (GC/MS) was used to evaluate the efficiency of the photocatalytic degradation of pollutants present in the oil field produced waters from Campos Basin, Rio de Janeiro, Brazil over TiO2 (anatase), in terms of organic loading reduction and acute toxicity removal observed in a previous publication. The effect of adding hydrogen peroxide has been investigated through an experimental design and found to be an adverse one. Two types of photocatalyst (Aldrich and Degussa P25) were used, and afterwards, their surfaces were investigated using scanning electron microscopy (SEM). The former showed an intense initial coverage by organic compounds and a severe corrosion with the use of hydrogen peroxide. The latter presented almost no initial coverage and was not corroded for small periods of photocatalytic treatment, also in the presence of the peroxide. (C) 2001 Elsevier Science B.V. All rights reserved.