The aim of this study is to present a methodology to calculate the exergy of lithium bromidewater solution (LiBr/H2O) widely used in absorption refrigeration systems, absorption heat pumps and absorption heat transformers. As the LiBr/H2O solution is not ideal, it is necessary to take into account the activity of the constituents in the chemical exergy calculation. Adopting the reference environment proposed by Szargut et al., the chemical exergy of pure LiBr was obtained as well as the chemical and physical exergy of the LiBr/H2O solution. Results are reported in the temperature range between 5 and 180 degrees C. In the literature, exergy values for LiBr/H2O solution are widely varied. This fact is due to different reference systems adopted to calculate exergy. Some cases in the literature are compared with that obtained with the methodology proposed in this study and with the approaches of Koehler, Ibele, Soltes and Winter and Oliveira and Le Goff. Copyright (C) 2010 John Wiley & Sons, Ltd.