Genetic improvement of quality traits of durum wheat achieved in Italy and Spain during the 20th Century was investigated using an historical series of 12 cultivars from each country. The European Union durum wheat quality index increased by 6.25% (0.13% year^–1 in Italian and 0.06% year^–1 in Spanish cultivars). Protein content decreased by ∼10% (–0.14% year^–1 in Italian and –0.19% year^–1 in Spanish cultivars) but protein per ha increased at a rate of 0.35% year^–1 (0.41% year^–1 in Spanish and 0.26% year^–1 in Italian cultivars). Yellow colour index increased by 9.9% (0.15% year^–1 in Italian and 0.10% year^–1 in Spanish cultivars). Test weight and vitreousness did not suffer significant changes over time. Gluten strength increased by 32.1% or 0.54% year^–1 in Italian, and 27.9% or 0.33% year^–1 in Spanish cultivars. Much larger genetic control on gluten strength was found in Italian than in Spanish cultivars. Changes in sedimentation index (41.1% or 0.64% year^–1 in Italy, and 41.6% or 0.49% year^–1 in Spain) were the consequence of the progressive incorporation into recent cultivars of favourable low molecular weight glutenin subunits (LMW-GS). Breeding increased the frequency of the LMW-GS combination aaa, which was present in 75% of all intermediate cultivars and in 100% of the modern Italian cultivars. A LMW-GS combination not previously reported (d?b) was identified in two modern Spanish cultivars. Breeding programs were also successful in increasing the stability of gluten strength and the sedimentation index.