Reexamination of geological, geophysical, and geochronological evidence suggests three principal conclusions. Firstly, the Kapuskasing line came into existence very shortly after the stabilization of the Superior Province. The upfaulting of strips of granulites and associated rocks, and probably the redistribution of densities in the lower crust responsible for the regional positive Bouguer anomaly, took place before the emplacement of the Matachewan dike swarm at ~2690 Ma. Secondly, relative movements along the line during this tectonic stage had an important sinistral transcurrent component and sinistral movements continued during the emplacement of the Matachewan swarm. Thirdly, displacements of various kinds took place on the Kapuskasing line during a number of later events spaced out over a period of more than 2000 Ma; some of their effects can be deduced from the relationship of regional dike swarms and of cratonic cover formations. These findings suggest that the Kapuskasing line did not originate as a rift structure. Analogies are seen with deep transcurrent shear zones of other continents.