The synthesis and deposition of the epicuticular waxes in barley are determined by the eceriferum (cer) loci. On the uppermost internodes, leaf sheaths and spikes of the wild type Bonus, the β-diketones and hydroxy-β-diketones (almost entirely hentriacontan-14,16-dione and 25-hydroxyhentriacontan-14,16-dione, respectively) are the predominating wax classes. In these same waxes esters containing alkan-2-ols (primarily tridecan-2-ol and pentadecan-2-ol) are present. Analyses of the β-diketone content and ester composition of waxes from Bonus and eight cer mutants led to the hypothesis that these two wax classes are synthesized from common precursors, namely C14 and C16 chain elongation intermediates. Subsequently, decarboxylation with a simultaneous retention of the carbonyl groups in the β-position would lead to the esterified alkan-2-ols while retention of two carbonyl groups plus further elongation would lead to the β-diketones. This closer biosynthetic relationship of the β-diketones to the esterified alkan-2-ols than to the other lipid classes-hydrocarbons, alkan-1-ol containing esters, aldehydes, alkan-1-ols and free acids—found in all barley waxes is illustrated schematically and the approximate sites of action of the cer loci indicated.