AbstractDue to the increasing complexity of materials processed in primary and secondary lead smelting, better control of impurity elements is required. In the present study, distributions of Cu, As, Sb and Sn between PbO–FeO–Fe2O3–SiO2 slag and Pb metal are characterized experimentally and analyzed using thermodynamic calculations. Experimental methodology involved closed-system equilibration of sample mixtures at high temperature followed by rapid quenching. The compositions of phases were measured using electron probe X-ray microanalysis and laser ablation inductively coupled plasma mass spectrometry. Thermodynamic calculations were performed using the FactSage software coupled with an internal thermodynamic database. Experimentally obtained distribution coefficients wt.% in slag/wt.% in metal at 1 200 °C (1 473 K) follow the sequence Sn >> Cu > As ≈ Sb at P(O2) < 10−9.5 atm and Sn >> As ≈ Sb > Cu at P(O2) > 10−8.5 atm. Model predictions are in good agreement with the experiment.