Abstract Over vast areas of the undeformed platform of southwestern Canada, the sedimentary cover of the ancient North American Craton is entirely of Phanerozoic age. In northwestern Canada, on the other hand, thick Proterozoic strata intervene between Phanerozoic deposits and crystalline basement (Fig. 4A.1). Even there, the preserved sediments contain only a fraction of the record of geological events that is preserved in the Foreland Belt of the Cordillera. Precambrian crystalline rocks beneath the sedimentary cover of the Interior Platform are dealt with in a separate chapter (Burwash et al., Chapter 3 in this volume). This brief treatment is largely a condensation of two chapters (“Middle Proterozoic”, and “Upper Proterozoic”) of the companion volume, “Geology of the Cordilleran Orogen in Canada” (Gabrielse and Yorath, 1991); it considers not only the Proterozoic sedimentary record of the undeformed basins and platforms, but also the more complete record preserved in the Eastern Cordillera. H. Gabrielse and M.E. McMechan have provided welcome assistance with fact and interpretation.