A simple model based on the network simulation method is proposed to estimate numerically the thermal conductivity of particulate reinforced metal-matrix composites. The estimation is carried out running the model in the standard Pspice code, the computing time being negligible. The 3-D solid is discretized in 1000 cubic volume elements which represent an acceptable approximation of the shape of the particles. For each reinforcement percentage and each combination of matrix and reinforcement more than 200 tests were carried out, so that the results may be considered close to the exact values. The limit values are scarcely influenced by the effect of the 3-D geometry and basically depend on the amount of the reinforcement. Applications to aluminum and titanium matrix composites reinforced with different types of particles are presented covering a wide range of reinforcement percentages.