Anti-GP-1D8 monoclonal antibody was produced in our laboratory. Immunoaffinity purification of GP-1D8 glycoprotein from human breast carcinoma tissues, on column with the monospecific antibody, is developed. The procedure permits purification of GP-1D8 to a highly purified state. It appeared as a single band in sodium dodcyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The molecular mass of GP-1D8 was determined to be 66 kDa by mass spectrometry. Its antigenicity was stable between 0 and 70 degrees C. It was breast cancer specific, as determined by immunohistochemistry and immunocytochemistry. The preparation of anti-GP-1D8 monoclonal antibody will facilitate further detection of, and functional study on, GP-1D8. The study also provides a simple, economical, and efficient method for affinity purification of target proteins from human or animal tissues.