In classical sugar factories, evaporation is one of the most energy intensive unit operations which mainly used for concentrating thin sugar juice. Replacing or combining this process with low energy consuming processes such as membranes could save large amounts of energy. There is no phase change in common membrane technologies and therefore they are low energy consumers. In the present study, a two-stage reverse osmosis system was investigated for pre-concentrating the sugar syrup. The energy consumption was compared for conventional evaporation versus reverse osmosis combined with evaporation. The obtained results represented several benefits such as significant energy saving and no thermal loss of sugar using the RO system. (C) 2007 Elsevier B.V. All rights reserved.