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The influence of high pressure on α-lactalbumin(ALA)/β-lactoglobulin (BLG) mixtures of various compositions was studied at pH 8.5 (50 mM Tris) by gel-permeation chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) without 2-mercaptoethanol. High-molecular-weight disulfide-linked protein oligomers formed at a pressure of 10 kbar (1000 MPa) if the weight fraction of BLG (W BLG 0) in the protein mixture exceeded 0.2. The maximum yield of these oligomers, of the order 80−85%, was observed at W BLG 0 ≥ 0.4. Conversion of both proteins in the oligomers was roughly the same. The estimates of the oligomerization yield obtained by gel-permeation chromatography and SDS-PAGE agreed well. SDS-PAGE results indicated that the formation of intermolecular disulfide bonds is necessary for the oligomerization. Thus, the oligomerization of pressure-denatured ALA and BLG is driven by thiol ↔ disulfide exchange in which the free thiol group of BLG acts as an initiator. Keywords: High pressure; α-lactalbumin; β-lactoglobulin; protein aggregation; gel-permeation chromatography; SDS-PAGE; intermolecular disulfide bonds; thiol ↔ disulfide exchange