A very important waste produced during the manufacturing of steel is the dust from the clectric arc furnace (EAF). This dust is emitted from the EAF with the rume gases. Because of its physical and chemical properties it is categorised as a hazarodus industrial waste. To prevent improper handling of this hazardous waste and stop or reduce pollution of the environment, and to find solutions for recycling of the EAF dust, it is important to carry out a systematic investigation of its physical and chemical characteristics, with a determination of its chemical and mineralogical composition, morphological characteristics and its interaction with the environment. In this article we report on the mineralogical, i.e., phase, composition of EAF dust determined with X-ray diffraction (XRD) analyses. The mineralogical phase in various grain size fractions of dust was identified on the basis of YRD patterns. The results of the investigation show that some phases appear in all samples and size fractions, some in most of the analysed samples and some only in individual samples. The results of the phase composition analysis will be of use both for a determination and explanation of the potential harmful impact of dust on the environment as well as in the selection of the most suitable method for managing and re-cycling the EAF dust.