Mesoporous carbon was prepared from the commercial activated carbon by steam activation with cerium oxide as catalyst. Steam activation with a catalyst loading of 0.5-2.0 wt% at 680-870 degreesC was examined. The surface area and pore size were evaluated by nitrogen adsorption at 77 K. and the structure of cerium oxide was characterized by XRD, XPS, and TEM. The results showed that the catalyst promoted the development of a mesopore at lower temperature (680-740 degreesC), and the mesopore was concentrated around 4-10 nm. The noncatalytic activation was advantageous in mesopore development and the catalyst would restrict the formation of mesopores at high temperature (800-870 degreesC). Higher loading of cerium oxide and higher activation temperature caused the aggregation of cerium oxide and then resulted in scattered pore size distribution. (C) 2003 Elsevier Inc. All rights reserved.