For the first time, the potential of polybenzimidazole (PBI) nanofiltration membrane as a forward osmosis membrane has been investigated. PBI was chosen mainly because of its unique nanofiltration characteristics, robust mechanical strength and excellent chemical stability. The MgCl2 solutions with different concentrations and other different salt solutions were employed as draw Solutions to test the water permeation flux through the PBI membrane during forward osmosis. High water permeation flux and excellent salt selectivity were achieved by using the PBI nanofiltration membrane which has a narrow pore size distribution. Effects of membrane morphology, operation conditions and flowing patterns of two feed streams within the membrane module on water transport performance have been investigated. It may conclude that PBI nanofiltration membrane is a promising candidate as a forward osmosis (FO) membrane. (C) 2007 Elsevier B.V. All rights reserved.