The expression and significance of p57KIP2, an important inhibitor of the cell cycle, remain unclear during carcinogenesis and during late metastasis to lymph nodes of tumors. To detail changes of p57KIP2 during colorectal carcinogenesis and during late metastasis to lymph nodes, p57KIP2, cyclin A, cyclin B1, cyclin E, CDK2, and Ki67 were immunohistochemically investigated in 22 specimens of normal mucosa, 62 of adenomas, 17 of carcinomas in adenomas, 189 of primary carcinomas, and 23 of lymph node metastases. Situated in nuclei, p57KIP2 expression increased significantly from normal mucosa to adenomas (p=0.0068), from mild through moderate to severe dysplasia in adenomas (p=0.0132). It significantly decreased from adenomas to unpaired primary carcinomas (p=0.0112) and from peripheral adenomas to paired central carcinomas (p=0.0018), but remained unchanged when primary carcinomas metastasized to lymph nodes (p=0.3401). p57KIP2 expression was not correlated with clinicopathological indices, but the patients having tumors without p57KIP2 tended to show a poor prognosis (p=0.0674). High p57KIP2 was significantly correlated with increased cyclin A (p=0.0007), elevated cyclin B1 (p=0.0007), reduced CDK2 (p=0.0021), and increased Ki67 (p=0.0013) in adenomas. Thus, loss of p57KIP2 expression appears associated with colorectal carcinogenesis.