We analyzed the expression of proliferating cell nuclear antigen (PCNA) in ectocervical sections fixed in formalin and embedded in paraffin using monoclonal antibody PC10, PAP and APAAP methods. A total of 156 cases was studied: 32 cases with normal epithelium, 33 cases with CIN I, 36 cases with CIN II, 55 cases with CIN III. We evaluated: 1. the index of PCNA (IPCNA), i.e. the proportion of PCNA-positive cells relative to all cells in the epithelium; 2. the IPCNA in each epithelial layer; 3. the epithelial height with PCNA-positive cells relative to the total height of the epithelium; 4. changes in the IPCNA with respect to the presence or absence of histological signs of HPV infection. We found: 1. a significant correlation between the index of PCNA and the severity of dysplasia in the whole epithelium and its individual layers; 2. a significant correlation between the epithelial height with PCNA-positive cells relative to the total height of the epithelium and the severity of dysplasia; 3. a lack of correlation between the IPCNA and HPV(+) and HPV(-) cases.