Vikings with artificially modified teeth have previously been documented in the south-eastern parts of Scandinavia and in England. In a project dealing with life in the Mälaren Valley in Sweden during the period AD 750–1100, new cases of people with modified maxillary teeth were observed. The hypothesis that the practice was entirely associated with adult men dating to the Viking Age was tested. The new cases demonstrate that the habit extended to eastern-central Sweden, including the proto-town of Birka, perhaps as early as in the middle of the eighth century. Additionally, cases from Sigtuna show that the practice may have ended as late as the beginning of the twelfth century. A microanalysis, using a scanning electron microscope, showed the heterogeneous character of the modifications. The affected individuals were all adult men, similar to previously published cases. Some of the men are associated with weapons and violent acts and the cases from Sigtuna were all from cemeteries with a possible association with lower social strata. However, discrepancies in archaeological contexts and in the characteristics of the modifications suggest temporal and spatial variation in the social meaning of the modifications.