The monoclonal antibody p105 (clone 780-3) recognizes proliferation-associated nuclear antigen p105 in conventionally fixed and processed histological materials. Formaldehyde solution-fixed and paraffin-embedded specimens excised from 184 patients with stage III squamous cell carcinoma of the cervix who were treated with radiation therapy alone were investigated for p105 positivity using an immunohistochemical method. Mitotic cancer cells were strongly positive for p105, showing cytoplasmic p105 positivity in almost all cases. The mean cytoplasmic p105 index was 2.02%, and the mean mitotic index in hematoxylin-eosin-stained preparations was 0.65%. There was a correlation between the cytoplasmic p105 index and mitotic index in hematoxylin-eosinstained preparations (y = 0.32x-0.003, r = .63). There was no significant relationship between the cytoplasmic p105 index or mitotic index in hematoxylin-eosin-stained preparations and prognosis. These results indicate that the cytoplasmic p105 index is not a predictive indicator for prognosis in patients with cervical squamous cell carcinoma, although this index is a more accurate mitotic index than the mitotic index itself in hematoxylin-eosin-stained preparations.