ABSTRACT. This study focuses on the resonance strategies of Sámi reindeer herders in four reindeer-herding cooperatives in northernmost Finland in climatically extreme years, specifically those occurring during the period 1970 -2007. "Resonance" is an instinctive and indwelling reaction of a herder to a specific change (in contrast to coping, which is a more general response). The study is based on interviews with herders, field experiences, reindeer population statistics, and weather data. Before the 1960s, herders were able to deal with changing weather conditions by using intensive herding techniques and semi-tame reindeer. After the 1960s, reindeer became wilder because of the use of snowmobiles and more extensive herding techniques. The herders of the fell and forest cooperatives did not have sufficient means to prevent the serious reindeer losses in 1972 -74, which resulted from two years of hard snow and ice cover, hot summers, and the free ranging of loose herds. In each of the four cooperatives studied, most of the old siida herds were combined, and one solution to handling large, loose herds was to build fences between cooperatives. Since the 1990s, all four cooperatives have used diverse herding and pasture rotation strategies to cope with the critical winter months. The herding techniques and the human-reindeer relationship in the fell cooperatives have differed from those in the forest cooperatives mainly because of differences in pasture types, topography, and microclimate. The contrast can be seen particularly in snow and ice conditions, as open fell regions have a thin and compact snow cover, whereas forest regions typically have deep, soft snow. This research shows that the resonance strategies of Sámi reindeer herders are both heterogeneous and dynamic: herders change them constantly, drawing on both old and new techniques to deal with the variable weather.