In this paper, a numerical study of the impact of the transport properties oil the condensation characteristics of certain refrigerant mixtures is presented. New correlations have been developed to calculate the thermal conductivity and viscosity of some alternative refrigerant Mixtures such as R-507, R404A, R-407C, and R-410A. In addition, new improved condensation correlations have been developed and presented for predicting the heat transfer coefficient and pressure drop. The results clearly showed that the condensation characteristics were well predicted using the newly proposed correlations with mean deviation of + 10 and 20% for the heat transfer coefficient and pressure drop respectively. Copyright (C) 2002 John Wiley Sons, Ltd.