Four different Cu-rich polymetallic concentrates (additionally comprising Zn, Pb and impurity elements As, Sb) from various deposits in Sweden are examined, in particular for the sintering tendency during roasting in inert atmosphere. Experiments performed in a laboratory-scale roasting setup between 200 °C and 700 °C in intervals of 100 °C revealed that significant sintering initiates from 500 °C for all four concentrates. Two sintering mechanisms are determined from the examination of the sintered calcines: (1) solid-state assimilation of Cu-, Zn- and Fe-bearing main sulphide minerals to form a high-temperature solid solution, the iss phase belonging to the Cu-Fe-Zn-S system; (2) low-melting liquid phase formation due to partial melting of galena facilitated by the presence of impurity-bearing minerals, mainly the arsenopyrite and Sb sulphosalts such as tetrahedrite. Galena also forms a melt below 700 °C with the iss phase. Therefore, the presence of galena in polymetallic concentrates generally increases the susceptibility to early sintering. These experiments in inert atmosphere facilitate a fundamental study with practical relevance to the roasting in low oxidation potential environments, favourable for volatilization of impurity elements such as As and Sb.