Quality data of eleven durum wheat genotypes grown under six environments in 1998-99 were evaluated to determine the relative effects of genotype and environment on quality characteristics, associated with protein content, SDS sedimentation test and mixograph parameters. Glutenin composition was also determined. The 11 durum wheat genotypes assessed, represented three Portuguese reference varieties and eight advanced breeding lines. Highly significant effects on quality parameters were detected, with the exception of protein content. Environment as well as genotype, had a significant effect on quality parameters, therefore, samples from multilocation trials should be used for quality evaluation, particularly in advanced breeding lines.