The purpose of our paper is to assess the hazardous potential of metallurgical solid wastes stored in a slag dump. We present the experimental procedures for determining chemical composition and for the leaching test of the 10 waste samples taken from the slag dump. According to the data obtained, in the composition of metallurgical solid wastes we identified the following compounds: manganese oxide (MnO), titanium dioxide (TiO₂), silica (SiO₂), total iron (Fe_total), alumina (Al₂O₃), lime (CaO), magnesia (MgO), lead oxide (PbO), zinc oxide (ZnO), chromium trioxide (Cr₂O₃), vanadium pentoxide (V₂O₅), and phosphorus pentoxide (P₂O₅). According to the leaching test, metallurgical solid wastes contain several heavy metals that can potentially be hazardous for all environmental factors (soil, water, and air). The content of hazardous heavy metals in the metallurgical wastes varies within the following limits: As (0.311-0.614 mg/L), Cr (0.192-2.514 mg/L), Mo (0.113-0.624 mg/L), Cd (0.104-0.479 mg/L), Pb (0.112-0.869 mg/L), Ni (0.112-3.212 mg/L), Zn (0.173-3.313 mg/L), and Hg (0.037-0.079 mg/L). From the point of view of the arsenic and mercury concentrations, the 10 samples of solid metallurgical wastes exceed the limit values for hazardous wastes.