Current western Canadian hard red spring wheat cultivars and their progenitors, inoculated with a composite of Tilletia tritici and T. laevis races, were grown at Lethbridge from 1989 to 1991 and the percentage infection was determined. This study also examined cultivar × environment interaction effects. Ancestral cultivars, such as Red Calcutta 33, Marquis, Thatcher, and their descendants, Canthatch, Park, Neepawa, Manitou, and Cadet, exhibited intermediate levels of bunt resistance. Cultivars including the cultivar Hope in their ancestry, such as Redman, Chris, Katepwa, Columbus, Reward, and Lancer, were highly resistant. Analysis of the environment × cultivar interaction indicated that bunt infection levels in Hope, Redman, and Columbus were stable over environments, but infection which varied according to environment was observed for Katepwa and Reward. The reduction of a number of cultivars including Neepawa, Thatcher, Kenya Farmer, Fortuna, Cadet, and Chris, was unstable across environment. Mexican semi-dwarf cultivars, such as Tobari 66, Potem 70, Cajeme 71, Ciano 67, Sonora 64, Inia 66, and the Canadian cultivars HY320, BW 90, and Laura, were highly susceptible. In general, the level of infection in these cultivars was uniform across environments. The nature of resistance in Canadian cultivars, the high infection levels of some Canadian cultivars and their Mexican semi-dwarf ancestors, and the variation in stability of infection levels of some cultivars across environments are discussed. Key words: Triticum aestivum, semi-dwarf, stability analysis, genotype × environment interactions