Pyrolysis and melting processes for municipal refuse treatment have been developed as an alternative of incineration process for decreasing several pollution problems caused in the incineration process. The plants of pyrolysis and melting process developed by Nippon Steel Co., Ltd. are already in operation at Ibaraki City and Kamaishi City. The plant based on purox process, one of the pyrolysis and melting process developed by showa Denko Co., Ltd. and Union Carbide Co., Ltd., started operation on November of 1981 at Chichibu City. For evaluating these pyrolysis and melting processes in terms of the alternatives of incineration process, the authors built the mass and heat model covering these processes based on gasification theory by use of experimental data of bench scale pyrolysis equipment and simulated the operation of plant by varying the operating factors. The model proposed by the authors was effective for evaluating the pyrolysis and melting process by comparing the simulation results and the observed operating data.