A thermodynamic model is presented to calculate N-2 solubility in pure water (273-590 K and 1-600 bar) and aqueous NaCl solutions (273-400 K, 1-600 bar and 0-6 mol kg(-1)) with or close to experimental accuracy. This model is based on a semi-empirical equation used to calculate gas phase composition of the H2O-N-2 system and a specific particle interaction theory for liquid phase. With the parameters evaluated from N-2-H2O-NaCl system and using a simple approach, the model is extended to predict the N-2 solubility in seawater accurately. Liquid phase density of N-2-H2O-NaCl system at phase equilibrium and the homogenization pressure of fluid inclusions containing N-2-H2O-NaCl can be calculated from this model. A computer code is developed for this model and can be downloaded from the website: www.geochem-model.org/programs.htm. (c) 2006 Elsevier B.V. All rights reserved.