Purpose: The p27Kip1 gene has been recognized as a negative regulator of the cell cycle and a potential tumor suppressor gene. Reduced expression of the p27Kip1 protein has been reported in several human tumors and has been associated with a poor prognosis in breast, lung, colon, prostate, bladder, esophageal and gastric cancers. In the present study, we assessed p27 expression in patients with colorectal cancer in relation to their clinicohistological parameters. Methods: We investigated p27 expression in 80 patients with colorectal cancers using immunohistochemical staining and the results were analyzed regarding the survival and clinicopathological parameters. Results: Among 80 cases of clolorectal carcinomas, p27Kip1 expression was detected in the nuclei of tumor cells in 48 cases (60%). With the exception of differentiation (p<0.01), no significant correlation was found between p27Kip1 and TMN stage, lymph node metastasis, depth of tumor invasion or overall survival. Conclusion: The results suggest that reduced expression of p27Kip1 protein plays a role in the differentiation of colorectal carcinoma and may be a potential prognostic factor. But, mare studies are reqired in order to determine whether p27Kip1 protein expression is a clinically valuable prognostic factor. (J Korean Surg Soc 2001;60:536-541)