At present, the Japanese government is promoting the construction of bigger incineration plants for urban refuse treatment to prevent a pollution by dioxins etc. Plant makers are also investing in technical research and development. In practice, however, the performance of plants is not always satisfactory, because the altered propertise and reduced quantities of refuse resulting from the strict selection of materials for recycling do not match the optimal values in the plant design. This report describes the system analysis by computer simulation for evaluation of the process system, and a discussion of refuse incineration and ash melting to slag through the experiences of plant operation in provincial cities.