The effect of high pressure treatment on whole egg white was examined using in vitro pepsin digestion and proteomic methods. Pepsin incubations conducted with an enzyme to protein ratio of 3:1 following high pressure treatment (400–800 MPa and 9 °C) resulted in increased hydrolysis of egg white proteins. Pressure treatment of egg white at 800 MPa resulted in greater susceptibility to pepsin hydrolysis than did thermal treatment at 95 °C. The effect of 800 MPa pressure treatment on egg white proteins was additionally examined by incubation with pepsin at an enzyme to protein ratio of 1:20 followed by 2-D electrophoresis. Results of these experiments showed extensive hydrolysis of most egg white proteins. Subsequent LC-MS/MS investigation of the low Mr fraction (< 3.0 kDa) derived from pepsin digested 800 MPa treated egg white contained numerous peptides previously shown to have bioactive and/or immunological properties.