Progress is reported toward development of a realistic and theoretically sound approach, enabling reliable predictions of membrane fouling in desalination processes. A significant amount of recent data obtained with typical organic foulants, in constant-flux and constant-pressure desalination, is revisited focusing on the dependence of specific fouling resistance a on permeate-flux J. Although clarifying quantitatively this dependence requires more work, these data suggest that, for the initial phase of fouling, a depends on J to a power greater than one. Furthermore, it is argued that a is the most appropriate fouling layer (intrinsic) property to both develop constitutive-type expressions relating fouling resistances to system variables (for predicting fouling evolution throughout membrane modules), and serve as a reliable indicator of feed-fluid fouling propensity. The advantages of resistance a for both applications are discussed; for the latter case, a simple parametric analysis of main process variables (flux, foulant concentration, membrane resistance R-m) shows that there is no single-value indicator (a or other) that can represent the fouling propensity of feed-fluids under all conditions (e.g. for both high-pressure and low-pressure desalination). Moreover, specific narrow ranges of resistance a values can be identified as criteria to assess membrane fouling for various desalination conditions. (c) 2013 Elsevier B.V. All rights reserved.