Membrane evaporation (ME) is a new membrane contactor process combining the advantages of osmotic evaporation and membrane distillation. It is based on the concentration of an aqueous solution by continuous evaporation through a metallic hydrophobic membrane able to be heated. The driving force of the process is the difference of water vapour pressure between a feed of an aqueous solution and a downstream flow of dry gas at low pressure. In the present paper, this new technique is developed with two different membranes and their performance in terms of evaporation flux is studied through the influence of air velocity and heat contribution. The objective of these introductory attempts is to validate this new concept; hence preliminary experiments have been realized with pure water. Then, a first approach to model this system and a comparison with experimental results have been carried out. (c) 2006 Elsevier B.V. All rights reserved.