The present study was performed to evaluate Ki-67 and B72.3 immunostaining in 20 selected cases of breast cancer. In particular, we have examined the intracellular localization of TAG 72 and the tumour growth fraction, identified by Ki-67 antibody, on frozen sections of mammary carcinoma, by immunohistochemical technique (ABC method sec.Hsu). Immunostaining of TAG 72 and Ki-67 antigen was related to histologic subtype, diameter, nodal involvement, and number of positive axillary nodes. The preliminary results suggest that: (a) the presence of Ki-67 nuclear staining appeared to be associated with a poorer degree of differentiation, but no direct relationships were observed with diameter and nodal involvement; (b) no correlation between Ki-67 labelling rates and B72.3 intracytoplasmic immunostaining was observed; (c) myoepithelial cells show weak intracytoplasmic positivities.