A comprehensive review of the application of group contribution (GC) models such as various forms of UNIFAC and the AFC correlation model for P-ow (octanol-water partition coefficient) calculations has been carried out. UNIFAC is an activity coefficient model, while AFC is a model specific for P-ow calculations. Five different versions of UNIFAC and the AFC correlation model have been compared to each other and to experimental data. The range of applicability of the GC models to P-ow is discussed, and general conclusions are obtained. A thorough analysis of the models was conducted including residual plots and numerical and graphical comparisons. We conclude that the GC concept has possibly exhausted its applicability to account for highly asymmetric systems, especially aqueous solutions with complex polyfunctional chemicals.