Geological, geophysical, chronological, and chemical data support the interpretation that terranes in Cape Breton Island correspond to those in Newfoundland, and that Cape Breton Island, like Newfoundland, preserves vestiges of the Laurentian margin and varied accreted terranes related to the "Gondwanan" continents. As in Newfoundland, the original relations among these accreted terranes and the timing of their accretion are enigmatic because of post-accretionary transpressive and transtensional adjustments. However, constraints are provided mainly by contrasts and similarities between now adjacent terranes. U-Pb geochronology reveals no links between the Humber-equivalent Blair River Complex and adjacent Aspy terrane until ca. 430 Ma, and isotopic studies do not show evidence for Grenville-type crust under Aspy terrane, even in the Devonian. Plutonism and high-grade metamorphism in the Blair River Complex and approximately synchronous volcanism and plutonism in the Aspy terrane may record juxtaposition by subduction. Devonian peak metamorphic conditions and syncollisional plutonism in the Aspy terrane are interpreted to reflect transpressional docking of the Aspy and Bras d'Or terranes, with the Bras d'Or terrane over-riding Aspy. Juxtaposition of the Bras d'Or terrane and Mira terrane (Avalon sensu stricto) was accomplished by the Early Carboniferous, but differences in Cambrian-Ordovician history indicate that at least the now-adjacent parts of the Bras d'Or and Mira terranes were not adjacent at that time.