High pressure treatment of solutions of P-lactoglobulin in the presence of microbial transglutaminase for 60 min at 40 degreesC resulted in an enzyme-induced oligomerization of the whey protein at pressures of 400 MPa and to a less extent at 600 MPa. The degree of crosslinking was lower when transglutaminase was added to solutions of P-lactoglobulin after high pressure treatment and no oligomerization was detectable when the protein was incubated with transglutaminase under atmospheric pressure. Thus, microbial transglutaminase in combination with high pressure treatment offers new perspectives for the modification of globular proteins, which usually are not affected by the enzyme under atmospheric conditions.