The combustion characteristics of pulverized Refuse-Derived Fuel (RDF) in a vertical type cyclone combustor were investigated. Experiments were carried out by evaluating performance at excess air ratios of 1.2 to 1.6, and combustion loads of 0.35 to 0.61 MW. It was found that pulverized RDF is a viable fuel and that its combustion characteristics can be effectively controlled and evaluated by the classical parameters used in current oil and coal combustors, under various conditions. The NO and CO emissions were examined to show the combustion characteristics and combustor performance under various excess air ratios and combustion loads. It was found that concurrent NO and CO reductions could not be achieved. CO reductions are achieved by changing the excess air ratio, which causes an increase in NO_χ levels. A stable combustion operating range can be determined by changing the excess air ratio and combustion load in terms of NO-O₂, CO-O₂ relationships. Further CO reduction can be demonstrated by changing the combustor exit nozzle diameter, which can contribute to stable combustion, but also increases NO emissions. The emissions of dioxins (PCDDs, PCDFs) were evaluated during start up and stable combustion. Very low dioxins levels of 0.019ng-TEQ/Nm³ were achieved with the cyclone combustor.