Wildfires have been and currently are an important factor in the northern ecosystems of all circumpolar countries. Historical accounts of fires are general and often provide few quantitative data; therefore, we must rely on more recent data from the fire suppression period to draw conclusions about fire frequencies. In this chapter data on the frequency of wildfires in northern Canada, Alaska, USSR, Sweden, and Finland are reviewed, and problems with the interpretation of fire frequency data are discussed. From the limited data which are available it appears that the patterns of fires at northern latitudes in the USSR are very similar to those observed in Alaska and Canada.