Irrigation and varietal improvement are two major ways of increasing and stabilizing durum wheat ( Triticum durum Desf.) production in semi-arid Mediterranean countries. A 3-year study was conducted in Khemis-Miliana (Upper Chelif, Algeria) to evaluate the yield response of six durum wheat genotypes to deficit irrigation. Grain yield in the unirrigated treatment ranged from 2.0 t.ha -1 (2008) to 2.8 t.ha -1 (2009). In rainfed conditions, the local variety Mohammed Ben Bachir (MBB) was the least productive (yield <2.0 t.ha -1) but the most stable, being the most insensitive to early drought. Yields of Bousselem exceeded 3.0 t.ha -1 whereas Mexicali and Vitron had more variable and lower yields. Rainwater productivity (RWPg, the ratio of grain yield to precipitation) ranged from 0.5 (MBB) to 1.1 kg.m -3 for Bousselem, Chen's, and Waha, three varieties known to be drought-tolerant. Deficit irrigation (140 mm) resulted in an increase in grain yield of 0.4 to 3.2 t.ha -1 depending on weather conditions and variety, with a mean response of 1.1 t.ha -1. Irrigating between shooting and booting increased straw production by 23% and grain production by 46% on average. The most explanatory components of final yield under rainfed management were the number of ears.m -2 and the number of grains per ear, while under irrigated management the number of grains per ear and the thousand grain weight were more critical for yield determination. The development of irrigation on durum wheat could help to close the gap between current and attainable grain yields in semi-arid Algeria, provided groundwater is available and the flowering period escapes desiccating hot winds. Wheat breeding should be focused on developing genotypes with stable behavior under drought but which respond well to irrigation.