This article discusses the available alternatives for ocean concentrate disposal, site specific factors involved in the selection of the most viable alternative for a given project, and the environmental permitting requirements and studies associated with their implementation. The article focuses on the three most widely used alternatives for ocean discharge of concentrate: direct discharge through new outfall; discharge through existing wastewater treatment plant outfall; and co-disposal with the cooling water of existing coastal power plant. Key advantages, disadvantages, environmental impact issues and possible solutions are presented for each discharge alternative. Results from recent salinity tolerance and toxicity study completed at the Carlsbad, California seawater desalination demonstration plant for a variety of sensitive marine organisms are presented. The practical implementation of this study along with other methods for analysis of the environmental impact of ocean discharges from large seawater reverse osmosis plants is illustrated with case study examples. (C) 2010 Elsevier B.V. All rights reserved.