Chromosomal location of resistance to two virulent Argentinean isolates of Septoria tritici was studied in two wheat ( Triticum aestivum L.) cultivars (Cappelle-Desprez & Cheyenne), a synthetic hexaploid (Synthetic 6x) and Triticum spelta in seedlings. Substitution lines of these (resistant or moderately resistant) genotypes into (susceptible) Chinese Spring were selected from a previous screening. For Synthetic 6x, resistance was clearly located in chromosome 7D. Chinese Spring with the 7D chromosome substituted by Synthetic 6x showed almost complete resistance, similar to the level of Synthetic 6x. For the substitutions with Cappelle-Desprez, Cheyenne, and T.spelta there were no lines with a behaviour similar to the resistant parent. However, some substitutions were more resistant than the susceptible parent suggesting that several chromosomes could be involved in the resistance of these genotypes to Septoria leaf blotch.