Radiocarbon-dated peat and peaty clay samples from geotechnical boreholes in the Canadian Beaufort continental shelf have been used to reconstruct a late Quaternary relative sea-level (RSL) curve. The samples were carefully selected and evaluated using palynological techniques, to ensure that reasonable age error limits could be given to each sample. The dated samples were then related to the local geological setting, using seismic profiles to determine the environment of deposition. The resulting data show a rise of 140 m in RSL since 27 000 years BP. A minor lowering of RSL at some time between 20 000 and 10 000 years BP is inferred from acoustic data. Contributions from basin subsidence, sediment loading, and consolidation account for 35 m of the total RSL rise. The RSL curve is interpreted in the light of recent models of the isostatic and eustatic responses of the Earth's crust at the Laurentide ice-sheet margin. Ice may have been more extensive during the middle Wisconsinan than previously thought and may have caused the major lowering of sea level in the shelf area. This ice may have advanced to within several hundred kilometres of the Mackenzie Delta – Tuktoyaktuk Peninsula coast. An ice readvance of late Wisconsinan age probably caused a subsequent minor lowering of RSL.