A magnetic anomaly in the Tåsjön-Ormsjön area of the Caledonian Front, central Sweden, has been studied. Its orientation discordant to Caledonian structures in the sedimentary cover requires a basement source probably related to a basic intrusion. Calculations of depth to the top of the magnetic source in the eastern part of the anomaly coincide well with depth to basement known from drillings. There is good agreement with new data from deep drilling further west in the Tåsjön area. This implies that the depth determination of ca. 600 m below sea level in the western area northwest of Lake Tåsjön probably indicates the surface of the crystalline basement beneath late Precambrian Risbäck Group sediments.