The environmental stability of breadmaking quality of wheat flours i.e. the absence of fluctuation across environments and genotype X environment interactions is as important as their performance in milling and baking. Many statistical approaches have been used to assess cultivar stability parameters across environments. Quality stability parameters were studied using a set of eleven bread wheat cultivars and five hybrid wheats grown in France at eight locations in two consecutive years. Three different statistical variances: ecovalence Wi, environmental variance S-Xi(2) and genotypic stability were used to assess the stability of quality parameters measured on wheat kernels at harvest, on the technological properties of their flours and on the molecular weight distribution of total endosperm proteins extracted using 2% SDS in phosphate buffer with sonication. Asymmetrical flow field-flow fractionation coupled with a multi-angle laser light scattering photometer allowed the molar masses of polymeric glutenins to be measured without size limits. Marked variation in the quality parameters was observed due to genetic and environmental effects. The three stability values calculated for protein content were not significantly correlated to the stability of the polymeric fraction, the bread loaf volume (LV) or the bread quality score (BQS). The three stability values of LV and BQS were significantly correlated to the stability of the weight-average (< M > w) molecular weight of the polymeric fraction. Multiple regressions showed that 60-84% of the stability values of LV and BQS were explained by the stability of only few quality parameters among which the (M)w of polymers played the major role.