In this communication, a reliable group contribution (GC) method is presented for the estimation of the thermal decomposition temperature (T-d) of ionic liquids. A dataset comprising experimental T-d data for 613 ionic liquids (ILs) that covers a temperature range from 374 to 740 K was collated from various literature sources. Approximately 80% of the dataset (T-d data for 489 ILs) was used to develop the model and the remaining 20% (T-d data for 124 ILs) was implemented to evaluate the predictive capability of the obtained model. The method uses a total of 30 substructures or structural functional groups to estimate the T-d. In order to distinguish the effects of the anion and cation on the T-d, 10 sub-structures related to the chemical structure of the anion, and 20 substructures related to the chemical structure of the cation were implemented. The results of this method show an average relative deviation (AARD%) of about 4.4% from dataset values. (C) 2013 Elsevier B.V. All rights reserved.