In order to enhance the performance of the vacuum membrane distillation process in desalination, i.e. to get more flux, it is necessary to study the effect of operating parameters on the yield of distillate water. Simple techniques including the normalized dimensionless sensitivity factor and temperature polarization coefficient as well as the solution of the transport models were used for this purpose. The sensitivity of the mass flux to the process operating parameters including downstream pressure, feed temperature, feed flow rate, and membrane permeability were investigated. The mass flux of distillate water was highly sensitive to the feed temperature especially at high values of vacuum pressure. The mass flux was more sensitive to the vacuum pressure at low feed temperature levels than at the high ones. Since lowering the temperature polarization coefficient is essential to enhance the process performance considerable efforts should be directed toward maximizing the heat transfer coefficient through better module design. The predictions of the normalized dimensionless sensitivity analysis were in agreement with the results obtained from solving the transport model of the process. (C) 2003 Elsevier Science B.V. All rights reserved.