A kind of TiO2 nanoparticles with uniform mesoporous networks was synthesized and then used to modify a graphite paste electrode (GPE). The electrochemical behaviors of p-chlorophenol at the GPE and the mesoporous TiO2-modified GPE were studied. Compared with the GPE, the mesoporous TiO2-modified GPE considerably increased the oxidation signals of p-chlorophenol, which was attributed to the regular mesoporous channels, large surface area, and high sorption capacity. The effects of pH value, amount of mesoporous TiO2, and accumulation time were studied, and a sensitive, rapid, and convenient electrochemical method was proposed for the determination of p-chlorophenol. The linear range is from 5.0 x 10(-8) to 5.0 x 10(-5) mol L-1, and the limit of detection is as low as 1.0 x 10(-8) mol L-1. Finally, the developed method was successfully used to determine p-chlorophenol in water samples. (C) 2009 The Electrochemical Society. [DOI:10.1149/1.3207946] All rights reserved.