This paper presents an experimental procedure to analyse the heat and mass transfer phenomena involved in osmotic membrane distillation and to measure the related parameters. Use is made of a module containing a few membrane sheets in co-current flow configuration. Whatever the inlet feed and extractant temperatures may be (equal to each other or not), the temperature difference between the two streams reaches an asymptotic value as the residence time increases. After the asymptotic conditions are established the module can be analysed as a pseudo-isothermal case.