Abstract: Objective:To study the significance of detection o f lymph node micrometastas is by immunohistochemical method with monoclonal anti-karatin antibody in patie nts with colorectal cancer.Methods:We examined 331 lymph nodes obtai ned from 47 colo rectal cancer patients who underwent a curative operation and diagosed by using immunohistochemistry SB techniques.Monoclonal mouse anti-keratin antibodies (AE1,AE1/AE3,AE3)were used as the primary reagents to identify tumor cells both in tumor tissues and lymph nodes.Results:A total of 36 micrometa stasis among 331 lymph nodes(11.9%) were found.Duke's C staging patients had more lymph nodes m etastasis than that in Duke's B staging patients(P<0.05).Postoperative fol low-up revealed that recurrence rate was high and the latent period of distant metastasis was much shorter in patients with occult mirometastasis th an those without.Conclusions:Even in histologically negative lym ph nodes,there i s a considerable possibility that micrometastasis may exist.The immunohistochemical detection of monoclonal anti-keratin antibody can explica te clinical staging a nd as an indication for colorectal cancer therapy.