The relationship between proliferating cell nuclear antigen (PCNA) expression and clinical stage, lymph node status, histological grade, malignancy index (MI) [13] were studied in 103 laryngeal squamous cell carcinomas (SCC). The PCNA index (the percentage of PCNA positive nuclei) was examined immunohistochemically using monoclonal PC10 antibody on paraffin sections. PCNA immunoreactivity was seen in all samples with mean value of PCNA index 37.4% for supraglottic and 36.8% for glottic SCC. The PCNA index was significantly related to histological grade and malignancy index (p < 0.05). For all tumors no correlation was found between PCNA index and clinical stage and lymph node status however, metastasizing glottic SCC had higher PCNA index than non-metastasizing ones. The modification of MI in glottic laryngeal SCC by adding PCNA index as a new parameter is proposed.