Objective: To study the relationship betweenproliferating cell nuclear antigen expression and itsmalignancy potential in colorectal carcinoma. Methods:Paraffin sections of 86 patients with advanced colorectalcarcinoma were assessed by immunohistochemical study,using a mouse monoclonal antibody (pc-10, DAKO -Co.USA) to check proliferating cell nuclear antigen (PCNA).TO compare PCNA with conventional clinicopathologicfactor including p53 overexpression, tissuecarcinoembnyonic antigen immunoreactivity patternand now cytometric DNA ploidy for assessing tumormalignancy potential. In addition, recurrence andsurvival of patients with advanced colorectal carcinomaafter curative resection were analyzed in accordancewith degree of PCNA expression. Results: PCNAlabeling index (PCNA-LI) increased significantly as thetumor stage advanced (p=0.0001). Strong correlationswere observed between PCNA-LI and variouspathologic parameters, including histologicdifferentiation (P=0.0027), lymphatic invasion(P=0.0001), vascular invasion (P=0.0001), lymph nodemetastasis (P=0.0001), and liver metastasis (P=0.0036).Mean PCNA-LI was also significantly higher in tumorwith DNA aneuploidy (P=0.0006) and negative (P=0.01).Linear relationships were demonstrated between PCNALI and clinical outcomes; Recurrence rate wassignificantly greater in the group with higher than themean PCNA-LI, who underwent curative resection(P<0.01), and three-year survival rates for curativecases with higher than the mean PCNA-LI weresignificantly poorer than those with lower than meanPCNA-LI (P<0.005). Conclusion: There werecorrelations between PCNA-LI and various pathologicparameters, PCNA-LI increased significantly as thetumor stage advanced in colorectal carcinoma, the ratesof recurrence and death got higher as PCNA-LIincreased after curative resection for colorectalcarcInoma. Objective: To study the relationship between proliferating cell nuclear antigen expression and itsmalignancy potential in colorectal carcinoma. Methods:Paraffin sections of 86 patients with advanced colorectalcarcinoma were assessed by immunohistochemical study, using a mouse monoclonal antibody (pc-10, DAKO - Co.USA) To check proliferating cell nuclear antigen (PCNA).TO compare PCNA with conventional clinicopathologic factor including p53 overexpression, tissuecarcinoembnyonic antigen immunoreactivity pattern and now cytometric DNA ploidy for assessing tumormalignancy potential. In addition, recurrence and survival of patients with advanced colorectal carcinomaafter curative resection were analyzed, Degree of PCNA expression. Results: PCNAlabeling index (PCNA-LI) increased significantly as the tumor stage advanced (p=0.0001). Strong correlationswere observed between PCNA-LI and variouspathologic parameters, including histologicdifferentiation (P=0.0027), lymphatic invasion (P =0.0001), vascular invasion (P=0.0001), lymph nodemetastasis (P=0.0001), and liver metastasis (P=0.0036).Mean PCNA-LI was also significantly higher in tumorwith DNA aneuploidy (P=0.0006) and negative (P =0.01).Linear relationships were demonstrated between PCNALI and clinical outcomes; Recurrence rate was significant significant greater in the group with higher than themean PCNA-LI, who underwent curative resection(P<0.01), and three-year survival rates for curativecases with higher than The mean PCNA-LI weresignificantly poorer than those with lower than meanPCNA-LI (P<0.005). Conclusion: There werecorrelations between PCNA-LI and various pathologic parameters, PCNA-LI increased significantly as the tumor stage advanced in colorectal carcinoma, the rates of recurrence and Death got higher as PCNA-LIincreased after curative resection for colorectalcarcInoma.