Published data on the initial Sr isotopic composition and range of SiO2content of some representative granites from the Swedish Proterozoic is reviewed. An attempt is made to divide these granites into genetic types related to partial melting of different source materials (igneous or I-type and sedimentary or S-type) and ultimately to the tectonic environment of magma generation. It may thus be possible to distinguish between magmatism initiated entirely within the crust, and magmatism initiated within or at the top of the mantle. Four groups of I-type granitoids can be recognised in the Swedish Proterozoic and these may possibly be related to three phases of subdaction of ocean floor. The second and third subduction phases were separated by a tensional phase possibly related to continental rifting and breakup. Granites of crustal origin can be recognised but are different from S-type granites from the type-area in southeastern Australia, not being depleted in Na and Ca. They were probably generated through the anatexis of Rb-rich volcanics and subordinate continental sediments in two different environments: (a) during regional metamorphism and (b) during regional uplift. This study suggests that both Andinotype and Hercynotype elements are represented in the Swedish Proterozoic and can be distinguished both in space and time. It gives strong encouragement to further critical and open-ended testing of the possibility that plate-tectonic processes were operative in the Proterozoic.