Nahanni National Park and the Mackenzie Bison Sanctuary are ecologically important areas in the Northwest Territories. Fire history data in Nahanni National Park and the Mackenzie Bison Sanctuary were used for a comparative analysis in order to identify the most influential characteristics of their respective fire regimes. The Mackenzie Bison Sanctuary is located on the Taiga Plains and is surrounded to the east and south by Great Slave Lake. Nahanni National Park is located in the Mackenzie Mountains, approximately 500 km west of the Mackenzie Bison Sanctuary. Elevation relief in the Mackenzie Bison Sanctuary is 160-260 m, and in Nahanni National Park is 180-2,640 m. Fuels are similar in both study areas and are dominated by low-density coniferous forest. Nahanni National Park has a significantly higher mean annual occurrence of very high and extreme classes of Canadian Fire Weather Index System codes and indices. Fire scar data indicate weighted mean fire return intervals (MFRIs) of 28 years and 27 years, respectively, for Nahanni National Park and the Mackenzie Bison Sanctuary. Area burned totals from a national database of fires greater than 200 ha in area suggest a fire cycle of 1,142 years and 199 years, respectively, for Nahanni National Park and the Mackenzie Bison Sanctuary. Differences in average fire size (1,149 ha in Nahanni National Park and 7,806 ha in the Mackenzie Bison Sanctuary) are partially attributed to topographic differences between the two areas. © 2004, Tall Timbers Research, Inc.