An integrated reverse osmosis (RO) + membrane distillation (MD) system where MD operates on the RO brine is considered for desalination processes. In particular, an energy and exergy analysis of the RO unit alone and coupled to the MD unit is presented in order to determine the energy requirements related to the integrated system with respect to the RO one. This energetic analysis coupled to the analysis of the overall performance of the two different systems led to an evaluation of the potentialities of the integrated membrane processes in desalination operations. The analysis has been tentatively extended to a complete membrane integrated system where nanofiltration (NF) has been also considered in the RO feed pretreatment.