The subject of the research was the geographic variation in tooth size and condylobasal skull length (CBL) in arctic fox Vulpes (Alopex) lagopus. The analysis was based on 328 skulls of individuals from 14 different populations. Most of the metric dental characteristics and CBL indicated a significant diversification among the populations. A particularly high inter»population variations was observed in the sizes of C¹, C₁, P⁴, and in the CBL. The arctic foxes of Eurasia were larger than the arctic foxes of North America. The largest specimens of the arctic fox were those of Komandorskiye Ostrava, while the smallest ones were on Baffin Land and Greenland. Moderate sizes of dentition and skulls were observed in continental populations (Taymyr, Ust-Yanskiy region, Zaliv Kozhevnikova, Yamal Poluostrov, Yakutskaya oblast'). As regards the variation in the size of the skull and dentition of arctic foxes, a higher variation was noted in arctic foxes from island (St. Lawrence Island, Komandorskiye Ostrava) and “coastal” populations (Yamal Poluostrov, Taymyr), and a lower one in arctic foxes from Asian populations (Zaliv Kozhevnikova, Yakutskaya oblast'). In the Arctic, within the geographical range of the fox, neither the size, nor sexual dimorphism of the metric dental and skull characteristics showed any specific geographic trend. However, the existing hypothesis, (such as Bergmann's rule, or “island syndrome”), do not explain the pattern of size variation in the arctic fox. The arctic fox morphological variation within its range is primarily shaped by climate conditions and food resources, and secondarily by competition within- and between species.