Introduction: The p16INK4a and Ki-67 biomarkers are used in cytology to help the detection of abnormal cells, due to their overexpression during the neoplastic transformation of cervix squamous epithelial cells. The expression of both markers in normal cells, is mutually exclusive, therefore, p16INK4a/Ki-67 dual-stained has shown high sensitivity and specificity in pre-malignant and malignant lesions. Objective: The aim of this study was to determine the simultaneous expression of p16INK4a and Ki-67 markers in conventional cervical abnormal cytology previously stored. Results: In 18 % of cases with high-grade squamous intraepithelial lesion, morphologically abnormal cells were positive for dual staining p16INK4a/Ki-67, as well as 5,6 % of cases of low-grade squamous intraepithelial lesions. All cases of atypical squamous cells of undetermined significance, atypical squamous cells suspicious of high-grade lesion, atypical glandular cells, adenocarcinoma, and squamous cell carcinoma were negative for the dual staining, but this last group was positive for p16INK4a and Ki-67 independently. Conclusions: These results are not consistent with expected, probably by environmental factors like pre-analytical conditions of process and storage of smears resulting in loss of antigenicity, or due to failure on random sampling that not allow generalize the findings to the population. It is necessary to make studies with randomized sampling, and standardize this technique in fresh smears or properly processed and stored, to consider the dual p16INK4a/Ki-67 staining as a useful technique to cytological interpretation with precision and accuracy.