The reclamation of effluents for irrigation and indirect potable water uses is rapidly developing as an alternative to seawater desalination. Two membrane-based options available to treat sewage for water reuse, tertiary filtration (TF) of the effluent from a conventional activated sludge (CAS) process and an integrated membrane bioreactor (MBR) are explored; in both cases, the level of treatment can be complemented by reverse osmosis (RO). These options are compared to desalination of seawater with both conventional multi-media membrane filtration. The capital costs for a plant producing water from seawater are about twice the costs of a plant reusing secondary sewage. Both the pretreatment costs and RO cost are higher. Similarly, the O&M costs for producing RO water from seawater are 2 times higher than the cost of reusing secondary sewage. The total life cycle costs for producing RO water from secondary effluent and seawater are 0.28US$/m(3) and 0.62US$/m(3) respectively.