The microwave stimulated immunodetection of a tumor associated antigen (TAG-12) by monoclonal antibody 7A9 and an avidin-biotinylated alkaline phosphatase kit was compared with the conventional staining method. No difference in the staining pattern of antibody 7A9 was noticed in serial paraffin sections of 50 specimens including normal, benign and malignant breast tissues after microwave irradiated and conventional immunostaining. The results demonstrate that microwave stimulated immunostaining gives reliable results and can remarkably reduce the time of the staining procedure.