Critical temperature (Tc) and critical pressure (pc) of the ternary mixture of ethylene + benzene + ethylbenzene (the mole ratio of ethylbenzene to benzene was fixed at 0.95:0.05) were measured by using a highpressure view cell with direct visual observation. The interaction coefficients obtained from the critical properties of the relevant binary systems were used to predict the critical properties (Tc, pc) of the ternary mixture. The agreement between the prediction and experiments is satisfactory.