A major problem for durum wheat production in the Mediterranean region is yield fluctuation, as a result of year to year variation in precipitation and heat stress during grain growth. Ten durum wheat cultivars differing in drought resistance were grown during 1998, both under rainfed and irrigated conditions in three sites of southern Spain. Vitreousness was positively correlated with TW (r equal to 0.48 asterisk asterisk) and semolina colour (r equal to 0.46 asterisk asterisk). An inverse relationship was found between grain yield and protein content. Regression of cultivar mean values of protein content and grain yield showed a negative relationship (r equal to - 0.724 asterisk asterisk asterisk) due probably to dilution of protein by non-nitrogen compounds and reduced starch accumulation in the grain under drought conditions.