Structural changes occurring during storage of oat globulin solutions containing 0 to 37mM sodium dodecyl sulfate (SDS) were examined by SDS polyacrylamide gel electrophoresis (PAGE). Oat globulin solutions stored with SDS (20mM) at room temperature showed dissociation of the oat globulin subunit (mean MW 58,000) into acidic (AP) and basic (BP) polypeptides of mean MW 36,000 and 22,000 respectively. This dissociation of subunits in the absence of a reducing agent (β-mercaptoethanol) was caused by a base-catalyzed sulphydryl-disulfide exchange reaction, since blocking of free sulphydryl groups by iodoacetate or N-ethylmaleimide prevented the dissociation of subunits. The changes emphasize the need to avoid extended storage before SDS-PAGE analysis of oat globulin and other proteins containing disulfide bonds and sulphydryl groups.