PCNA (proliferating cell nuclear antigen) is a cell cycle related protein that is maximally elevated in late G1 and S-phase of proliferating cells. 114 biopsy specimens of colorectal cancer were immunolabeled with PC 10 which specifically recognizes PCNA; Dukes' staging and histological grading were estimated for each case. All patients were followed-up for at least 60 months or to death. All data were analysed by the computer program NCSS (Number Cruncher Statistical System). According to the results, PCNA-index may be considered an independent prognostic factor for colorectal cancer; it may also be helpful in supporting the therapeutic strategies based only on Dukes' stage.