Abstract: BACKGROUND ＆ AIM： To determine the different expressions of P73 and P51 genes in breast cancer. MATERIALS AND METHODS： The expressions of P73 and P51 gene in breast cancer tissues were assessed by RT_PCR and terminal deoxynucleotidyl transferase biotin_dUTP nick end labeling(TUNEL)and the relationship between the two genes and apoptosis were analysed. RESULTS： The difference in the expressions of P73 and P51 genes was significant in breast cancer(P<0.05). There was no statistical significance between these two gene expressions in breast fibroadenoma (P>0.05).The difference in the expressions of P73 and P51 genes was significant in those without lymph nodes metastasis(P<0.05), but not in those with positive nodes.Also, there was no significant difference between the expressions of P73 and P51 genes in ER_and PR_positive breast cancer and ER_and PR_negative breast cancers(P>0.05). The apoptosis rate cancer cells with P51 gene was not significantly different from those with p73 gene.The same was true for cancer cells without either gene. CONCLUSION: The expression of P73 gene was higher than that of P51 gene in breast cancer. P73 gene may play a more important role in breast carcinogenesis than P51，especially in the early stage of tumor. But the pathogenesis needs further studies.

Key words: P73, P51, breast cancer, apoptosis, RT_PCR