The immunohistochemical staining for the C-erbB-2 oncoprotein was performed on sections from paraffin embedded tissue blocks of 96 primary breast cancer patient who underwent operation in our hospital, in order to evaluate the significances as a prognostic factor in the human breast cancer. We investigated the correlation between traditional prognostic factors-patient age, primary tumor size, axillary lymph node metastasis, pathological grade, hormonal receptors (ER&PR)-and C-erbB-2 oncoprotein overexpression. The overall rates of positive staining of C-erbB-2 oncoprotein was 37.5% (36/96), Statistically, the C-erbB-2 positive staining was not correlated with patient age, primary tumor size, axillary lymph node involvement, hormonal receptors. But the high pathologic grade was correlated with C-erbB-2 oncoprotein overexpression and appeared statistically significant (p=0.010). The C-erbB-2 oncoprotein appeared to have prognostic significance in human breast cancer from the result.