This paper will compare two types of thin-film composite membranes with different chemistries. Both types are produced by a process known as "interfacial polymerization", but the two have different barrier layer chemistries. One type is manufactured using the chemistry protected by the Cadotte patent and is classified as a polyamide. The other type utilizes a new chemistry that forms a polyamide-urea barrier layer. This new barrier layer has proven superior in critical areas of reverse osmosis operation including rejections of certain dissolved species and its fouling-resistant property. These benefits, along with others, will be explored by reviewing three plants with long histories of fouling problems. Operational data from before and after the introduction of this new membrane will be presented along with interviews conducted with the engineer and/or supervisor of each location. It is this information that will differentiate this new polyamide-urea thin-film composite membrane, not only in chemistry, but, in the field where money and time can be saved.