In this research, the degradation of Acid Red 274 (AR 274) was investigated under subcritical water conditions using H2O2, which led to the oxidative degradation of Acid Red 274 up to its 80% of mineralization. The Box-Behnken design matrix and response surface methodology (RSM) were applied in designing the experiments for evaluating the interactive effects of the three most important operating variables. Thus, the interactive effects of temperature (100-250 degrees C), oxidant (H2O2) concentration (50-250 mM), and time (30-60 min.) on the degradation of AR 274 were investigated. A total of 17 experiments were conducted in this research, and the analysis of variance (ANOVA) indicated that the proposed quadratic model could be used for navigating the design space. The proposed model was essentially in accordance with the experimental case with correlation coefficient R-2 = 0.9930 and Adj-R-2 = 0.9839, respectively. The results confirmed that RSM based on the Box-Behnken design was a compatible method for optimizing the operating conditions of AR 274 degradation. (C) 2011 Elsevier B.V. All rights reserved.