Over the past 40 years, severe population fluctuations in Peary caribou (Rangifer tarandus pearyi) and muskoxen (Ovibos moschatus) living in the High Arctic of Nunavut has caused widespread concern. In order to better understand these fluctuations, patterns of population characteristics need to be examined. The best source for long-range information is from Inuit, who have interacted with these species on a regular basis over the long-term. This thesis presents the collection and documentation of observations by Inuit to describe the population distribution of caribou and muskoxen. Interviewees also shared their understanding of factors contributing to changes in abundance, and information concerning the ecology of these species. Interviewees from Resolute Bay have observed severe fluctuations in the abundance of caribou on Somerset, Prince of Wales, Russell, Cornwallis and Bathurst Islands and northern Boothia Peninsula. Interviewees from Grise Fiord indicated that changes in caribou populations on Devon and southern Ellesmere Islands have occurred but have not been substantial. Interviewees also indicated that the populations of muskoxen on Somerset, Prince of Wales, Devon and Southern Ellesmere Islands have increased, whereas muskoxen populations on Cornwallis and Bathurst Islands have been consistently low. Overall, interviewees expressed that changes in caribou and muskoxen populations are normal. However, interviewees continue to be concerned with the possibility of negative impacts caused by significant human disturbance (e.g., petroleum exploration). They also suggest that factors such as weather, presence of forage and the handling of animals influence the distribution, abundance and health of caribou and muskoxen. Interviewees also described the variability in the physical traits of Peary caribou throughout the High Arctic islands. Generally, from Boothia Peninsula to Bathurst Island the bones of caribou become smaller and their fur has a finer texture. On the islands north of Bathurst Island the features that are unique to Peary caribou become more pronounced. Interviewees also explained that overall, caribou are not negatively impacted by wolves and that a large abundance of muskoxen is often followed by the decline in the population of caribou in a specific area. The documentation of this information contributes to our understanding of two unique northern species, and has the potential to aid in shaping the management of human activities that may affect them.