The photocatalytic oxidation of phenol and chlorophenols were studied in the presence of ZnO in a batch reactor configuration illuminated with a 6 W low pressure mercury lamp. The variables studied include catalyst usage, solution pH and phenol concentration. The degradation rate of phenol was favourable in the neutral pH range. However, o-chlorophenol and p-chlorophenol undergo degradation at a faster rate at lower pH values. The disappearance of phenols in each case approximately obeyed first-order kinetics with the apparent first-order decay constant increasing with decreasing solute concentration. Total organic carbon analysis indicated complete mineralisation of phenols on ZnO surface. (C) 2004 Published by Elsevier B.V.