In this paper, the response surface methodology is applied to optimize the operating conditions of mu DMFC (micro direct methanol fuel cell). Three operating parameters, the methanol flow rate, the methanol concentration and the cell temperature are considered in this study, and the ranges of them are 0.5-1.5 ml min(-1), 0.5-2.0 mol L-1 and 20-60 degrees C respectively. The individual effects of these operating parameters and the combined effects of multiple operating conditions on air-breathing cell performance are examined. Furthermore, a quadratic model is established to describe the maximum power density and open-circuit voltage as the response value. (C) 2014 Elsevier Ltd. All rights reserved.