The flash processing of electric arc furnace (EAF) dusts is a promising method for recovering zinc and producing nontoxic slags for direct disposal. In order to reduce the zinc content of the dust particles and maintain the iron content in oxide form, a certain range of temperature and oxygen potential must be provided, as dictated by thermodynamic requirements. Experiments were conducted with EAF dusts at three levels of zinc concentration in an electrically heated flash reactor. The results showed that the CO:CO2 ratio in the process gas was the most important parameter. The effects of zinc content in dust and O2 in inlet gas on zinc recovery were secondary. Toxicity leach tests showed that the resulting slag, even at low zinc recovery, can be disposed safely as landfill.