The paper presents the results of new measurements of the phase behavior of the ternary system methane-n-hexane-n-tetradecane. The measurements have extended over the range of compositions at 348.15 K and 383.15 K for pressures from 2 MPa up to the vicinity of the critical pressure of around 25 MPa. As well as the phase envelope itself, measurements of the density of both phases have been carried out simultaneously. The experimental data provide the opportunity to examine the effectiveness of three different thermodynamic models for the prediction of the properties of ternary mixtures from prescribed information on the constituent binary systems. The models employed for the tests include the cubic equation of Peng-Robinson, the one-fluid corresponding-states model and the more flexible, multiple-reference fluid corresponding-states model. It will be shown that only the multiple-reference fluid model provides a satisfactory description of the fluid density. The same model also represents the phase compositions moderately well, but not quite as well as the Peng-Robinson equation. (C) 1998 Elsevier Science B.V. All rights reserved.