Abstract Permian rocks are preserved throughout most of the eastern Cordillera and locally, in the Peace River-Liard River area, on the Interior Platform (Fig. 4F.1, 4F.2, 4F.3). They are absent from the remainder of the Interior Platform and from most of the Mackenzie Mountains through truncation at several disconformities beneath Mesozoic strata. Permian sediments were deposited mainly along the margin of the North American plate in a Permian depositional basin, here named Ishbel Trough, extending from the 49th parallel to the Ancestral Aklavik Arch in northern Yukon Territory. The trough occupies approximately the same position as the Carboniferous Prophet Trough (Richards et al., Subchapter 4E in this volume). In the Peace River-Liard River area, Permian sediments were also deposited on the western cratonic platform. The western margin of Ishbel Trough has not been identified. It (Fig. 4F.2, 4F.3) may have been in the area presently occupied by Cariboo Terrane (Struik and Orchard, 1985; Struik, 1986), which lacks Permian strata and may have been partly subaerially exposed during the Permian Period. A marginal basin to the west of Cariboo Terrane (Barkerville Subterrane of Kootenay Terrane; Monger and Price, 1979) contains a remnant of Permian strata (Sugar Limestone). The eastern margin of Ishbel Trough was a broad hinge-line along the western margin of the cratonic platform. In northeastern British Columbia and southwestern District of Mackenzie the hinge coincided with a zone of normal faulting, but generally the position of the eastern trough margin is unclear, because of eastward truncation of Permian strata (Fig. 4F.2, 4F.3).