Cyclicity in population fluctuations has been described in a number of tetraonid species. Also, synchrony in these fluctuations – both between and within species – has been found in several bird species and other animals. The present study analyses data of the northernmost subspecies of Rock Ptarmigan Lagopus mutus captus in Greenland. The material has been collected by the Danish military dog sledge patrol Sirius in North and Northeast Greenland during the period 1977-2006. The material from three of the subareas was of sufficient quality for statistical analyses. Additionally, we present data from the Zackenberg Research Station and the Karupelv Valley Project within the same general study area. We checked for cyclicity in the population fluctuations by testing the significance of the parameters in an autoregressive log-linear model fitted to the time series, but failed to detect cyclicity in any of the time series. Some level of synchrony in population fluctuations between neighbouring subareas was detected, although this was statistically significant in only one pair of neighbouring subareas.