Abstract The paper discusses recent activities in seawater desalting by reverse osmosis at the OWRT Wrightsville Beach Test Facility. Design, operation and performance of pretreatment plants and reverse osmosis plants are discussed in the paper. Performance of two types of membranes are described. A thin film composite cellulose triacetate-cellulose nitrate-cellulose acetate membrane produced 12.1 gfd (gallons per square foot per day) product with an initial TDS of 140mg/l. The second membrane tested was a polyamide type which produced 20 gfd product with an initial TDS of 500 mg/l. A 432,000 gpd central pretreatment plant provides feed to most RO plants on the site and includes clarifiers, dual-media filters, greensand filters and a carbon filter. The clarifiers require 25 mg/l alum for formation of settleable flocs. Filtrate from the greensand filters has a turbidity of O.1 – 0.2 FTU and an average 15 minute-plugging index of 45%.