Proterozoic molybdenite occurrences in Sweden are spatially associated with acid volcanics. To test if mineralization is caused by remobilization of molybdenum in such rocks, fifty samples from northern Sweden have been analysed for major elements and 15 trace elements. Volcanics from the mineralized Rappen district and Vidsel area, situated on the Proterozoic continental domain north of the Skellefte district, have lower Mo-contents than the calc-alkaline submarine Skellefte volcanics. It is therefore concluded that acid volcanics are not the source for molybdenum mineralization. The association between molybdenite occurrences and acid volcanics in northern Sweden is tectonic, suggesting that the late orogenic development of the Rappen district and the Vidsel area, characterized by block movements and development of rift systems, is favourable for generation and emplacement of the granites responsible for molybdenite mineralization.