In this paper, a detailed analysis of the performance and trends of predictions of vapour-liquid phase equilibrium with the UNIFAC-CI model, employing a method to predict missing group interaction parameters (GIPs) through the use of connectivity indices, are presented. The cases where the model using the predicted GIPs perform well and cases where the performance is unreliable are investigated. The causes for the unreliable performance of the UNIFAC-CI model are explained and results from one of the remedies that gave very good results are presented. The extrapolation features of the UNIFAC-CI model with the predicted GIPs in solid-liquid phase equilibria calculations involving precipitation of organic chemicals are also presented. Finally, the application of the GC(Plus) approach to reference modified UNIFAC (Dortmund) model is presented in terms of new and extended parameter tables. (C) 2010 Elsevier B.V. All rights reserved.