The disseminated copper ore deposit at Aitik in northern Sweden has been studied by means of sulphur and strontium isotopes. The δ34S values are around zero relative to CDT for all sulphides (pyrite, chalcopyrite, pyrrhotite) and about + 10% for barite, indicating that the ore body is homogeneous with respect to sulphur isotopes. The sulphur isotope data indicate a temperature of formation around 500 °C and a magmatic hydrothermal origin of the Aitik ore. The strontium isotope data of barite show an increase in87Sr/86Sr from the center of the ore body (0.7045) towards the hanging wall (0.7160) and the footwall (0.7069). This increase is possibly due to the contribution of radiogenic Sr from the bedrock. The lowest Sr values, together with the spread in values across the ore, support the hypothesis of a primary hydrothermal origin for the ore.