A numerical model was developed to describe the performance of a full-scale reverse osmosis desalination process used for wastewater reclamation, in which fouling was a major operational concern. Key feed water quality parameters such as total dissolved solids, total solids, and solids size distribution were determined to assess the nature of foulant matter. Membrane separation and fouling parameters were determined using membrane transport theory, pilot plant performance data, and autopsy of clean and fouled membrane elements. The data was input into the numerical model, which used basic momentum and mass transport equations to relate membrane fouling kinetics to the transient pressures, flows, and concentrations occurring throughout the full-scale system. The model results are compared to data obtained from the RO pilot plant treating secondary wastewater. Results confirmed that the pilot plant behavior was well predicted by the numerical model, which suggests that full-scale RO performance and fouling kinetics may be predicted. Laboratory, pilot, and full scale design phases for future RO processes may be significantly streamlined by adopting these procedures. Includes 4 references, figures.