Interfacial tension values of two liquid-liquid-vapour systems, a ternary water-decane-methane and a quaternary water-cyclohexane-decane-methane, were measured using a pendant drop technique at 150 C and high pressures up to 28.1 MPa. The tested ternary mixture showed a maximum liquid-liquid interfacial tension by increasing pressure whereas it only slightly increased liquid-liquid interfacial tension in the quaternary system. The predicted interfacial tension values by some models are compared and the application of liquid-liquid interfacial tension models for predicting the liquid-vapour interfacial tension at high pressure conditions is discussed. (c) 2007 Elsevier B.V. All rights reserved.