The Valderrama modification of Patel-Teja equation of state (VPT EoS) has been extended to predicting fluid phase equilibria in the presence of single and mixed electrolyte solutions at high-pressure conditions. Salts have been introduced as components in the EoS by calculating their EoS parameters from corresponding cation and anion parameters. A non-density dependent mixing rule is used for calculating a, b, and c parameters of the EoS. The inclusion of salts in the EoS resulted in the omission of the Debye-Huckel electrostatic contribution term in the fugacity coefficient calculations. Water-salt binary interaction parameters (BIPs) are optimised using freezing point depression and boiling point elevation data of aqueous electrolyte solutions. Gas solubility data in aqueous electrolyte solution are used for optimising salt-gas BIPs. The predictions of the model have been compared with independent experimental data, demonstrating the reliability of the approach. (C) 2003 Elsevier Science Ltd. All rights reserved.