The influence of the malting barley genotype on the apparent attenuation limit (AAL) was investigated. The AAL level correlated closely with the maltose concentration in the wort but was not affected by other fermentable sugars or by the total carbohydrate content. The chemical composition, modification, amylolytic enzyme activities and several starch properties of selected malts were studied in detail. Variations in the maltose concentration could almost solely be traced back to genotype-dependent disparities of β-amylase thermostability. These differences are due to interallelic polymorphisms of the β-amylase gene and are easily detected by PCR. Hence, PCR primers offer remarkable prospects for breeding barley on the basis of a marker-assisted selection (MAS).