Today MSW incineration is still the preferred option for waste reduction in densely populated areas, but under heavy and sometimes irrational public pressure it has gradually been confronted with more and more stringent emission codes. As a consequence, its acid gases, dust, heavy metal and dioxins emissions have become marginal or even negligible. To achieve this purpose, however, most existing plant required extensive revamping and extension, which led to a large number of design options and operating problems, some of which are discussed in this paper.