Background. A polyclonal antihuman c-erbB-2 oncoprotein antibody recognized c-erbB-2 oncoprotein in routinely formaldehyde-fixed, paraffin-embedded specimens. Methods. Specimens taken from 192 patients with Stage III squamous cell carcinoma of the cervix treated with radiation therapy alone were investigated for c-erbB-2 oncoprotein expression using an immunohistochemical method. Results. Cancer cells that were positive for c-erbB-2 oncoprotein showed a surface membrane staining pattern. Of the 192 patients, 143 were negative for c-erbB-2 oncoprotein, 12 were weakly positive or ambiguous, 31 were positive, and 6 were strongly positive. The 5-year survival rate of the 155 patients who tested c-erbB-2 negative or weakly positive was significantly better than that of the 37 patients whose results were positive or strongly positive (61% versus 41%, P = 0.022). Conclusion. c-erbB-2 Oncoprotein expression in cancer cells may imply a poor prognosis for patients with Stage III squamous cell carcinoma of the cervix treated with radiation therapy alone.