Abstract An air mass-based synoptic climatological approach is used to determine if the frequency of occurrence of the coldest and mildest air masses at seven stations in the Russian Arctic has changed and if the physical character of these air masses have shown signs of modification over the past 40 years. It has been suggested that a detected increase in surface temperatures over the past 40 years within the coldest air masses in the western North American Arctic may be attributed to the shorter residence time of these air masses through the time period. A re-evaluation of the data at two of the stations in the Alaskan and Yukon Arctic indicates that a long-term warming is, in fact, taking place even when residence time is kept constant. Results for seven additional Russian stations are less conclusive, and they do not exhibit a consistent statistically significant warming. It is possible that changes in the physical character of these very cold air masses are due to factors other than residence time, such as anthropogenic influences.