The effects of pasteurization, lyophilization, and freezing on immunoglobulin and lymphocytes in human milk was studied. We found a significant decrease in total lymphocyte count after all three processing methods. Pasteurization and lyophilization caused a significant decrease in immunoglobulin concentration and in specific antibody titer to Escherichi coli. Freezing specimens up to four weeks resulted in no significant alteration of IgA content or in E. coli antibody titer. Since a major advantage of human milk is the transference of passive local immunity, these quantitative changes may have clinical importance.