The UV/H2O2 process has often been proposed as an effective treatment technology for remediation of colored wastewaters. However, it has frequently been noted that it is not as economically efficient as other treatment technologies. To limit this drawback as much as possible, an effort to optimize the treatment technology from both the economical and operating points of view is needed. This paper presents a study on determination of cost optimal operating conditions for decoloration and mineralization of C. I. Reactive Blue 268 by the UV/H2O2 process. Dye concentration, hydrogen peroxide concentration, pH, treatment time, and temperature were considered to be influential operating parameters. Cost of electricity, cost of hydrogen peroxide, and cost of water needed to adjust the dye concentration were considered to be relevant operating costs. The presented approach is based on response surface methodology in conjunction with mathematical programming. The results obtained clearly indicate that, in order to assure effective and economically efficient operation, the UV/H2O2 process should be simultaneously optimized from the perspective of both operational and economic efficiency. (C) 2009 Elsevier B.V. All rights reserved.