Three phases, hydrate-liquid water-vapor (H-L-w-V) equilibrium temperatures for the gas (single/mixture) hydrate in presence of inhibitors such as methanol (MeOH) and mono-ethylene glycol (MEG) have been predicted. The model is based on equality of water fugacity in the liquid water and hydrate phases. The van der Waals and Platteeuw model is applied for calculating the fugacity of water in the hydrate phase. The Stryjek and Vera modification of Peng-Robinson (PRSV2) equation of state is used to evaluate the fugacity of water in the vapor and liquid phases. To achieve more accurate results, binary interaction parameters are adjusted as a linear function of temperature. The Langmuir constants are demonstrated as a function of temperature by using genetic algorithm. Acceptable agreement between the model predictions and experimental data exhibits its reliability. (C) 2012 Elsevier B.V. All rights reserved.