The behavior of different reverse osmosis membranes, namely, HR98PP, SEPA-MS05, and DESAL-3B, was compared with the one predicted by a solution-diffusion model. This model assumes that the membrane has a homogeneous, nonporous surface layer and uses two main parameters, permeate concentration C-p and volumetric permeate flux Q(p), to characterize the membrane system. In order to calculate these parameters, the theoretical values of water and solute permeability constants, A(w) and B-s, and the osmotic pressure coefficient, Psi, were initially determined. Using the software Sigma Plot V 10.0, accurate values of Psi, Q(p), and C-p were only obtained for the DESAL-3B membrane, i.e., the selected solution-diffusion model can be applied to this membrane.