AbstractSynthetic hexaploids (SH) developed at the International Maize and Wheat Improvement Center (CIMMYT), involving fourTriticum turgidumand nineT. tauschiiparents, were evaluated for resistance to Karnal bunt (KB)(Tilletia indicaMitra) during three crop seasons over three years at Ciudad Obregon, Sonora, Mexico. Ten tillers of each SH at boot stage, taken at random, were injected with a suspension of sporidia in water (10,000 spores/ml of water). At maturity the inoculated spikes were threshed individually and evaluated for the percentage KB‐infected grains. Based on the mean KB score of each entry for three seasons, 49 % of the SH were immune (0 % infection) to KB. Highly resistant expressions characterized the SH which appeared to be influenced by the resistance of theirT. turgidumand/orT. tauschiiparents. The overall mean infection of the SH wheats was 0.24 % compared to 56.14 % in the susceptible bread wheat check cultivat ‘WL711’. Transfer of KB resistance genes from SH wheats into bread wheat is currently underway at C