A full-scale (8-cubic feet/second) reverse osmosis (RO) water treatment plant equipped with conventional cellulose acetate (CA) membranes, and two pilot RO plants, equipped with polyamide (PA) membranes, were tested for their ability to remove total organic carbon (TOC) and a broad range of trace organics, including volatiles, purgeables, neutrals, bases, phenols, and acids from lime-clarified secondary municipal wastewater. Total organic carbon was removed to the extent of 89 percent by the CA membrane and to 99 percent by the two PA membranes. The three membranes tested removed trace organics to varying degrees, depending on the structural features of the compounds, such as charge, size, and branching. Ranges of removals of volatiles, purgeables, and extractables by the full-scale RO plant at 84 percent water recovery were 53-87 percent, 0-100 percent, and 73->98 percent, respectively. The two membranes tested showed significant differences in their ability to reject trace organics. All membranes rejected branched, complex molecules but varied in their rejection characteristics for smaller molecules, such as chlorinated solvents. The latter group was rejected to a varying degree by polyamide membranes but passed through cellulose acetate membranes. The use of RO for trace organics removal is evaluated by comparing cumulative removals of different schemes with and without RO treatment. Includes 25 references, tables, figures.