Experimental thermal conductivities were established for the methane-carbon dioxide system using a coaxial cylindrical cell. These measurements were carried out on pure methane, carbon dioxide, and three binary mixtures containing 0.755, 0.464, and 0.243 mole fraction of methane. The temperatures of this study ranged from approximately 60° to 160°C and pressures extended up to 10000 psi. The resulting thermal conductivities h for the dense gaseous state and the corresponding thermal conductivities of the dilute gas at atmospheric pressure, k*, for this binary system were used to produce the unique relationship for this system, (k*- k*) λze5=3.075 × 10-8[exp (1.203PR) - exp (- 4.359 PR2) ], where the thermal conductivity parameter, λ=M1/2 Tc1/6/Pc 2/3. For the mixtures of this system, pseudocritical constants were used. This relationship was applied for the calculation of thermal conductivities which, when compared with corresponding experimental values, produced an average deviation of 2.24% for 220 experimental points considered.