Despite R0-resection up to 30% of patients with colorectal cancer stage UICC I and II die of recurrent disease. This tumor progression could be caused by isolated disseminated tumor cells in lymph nodes which are not detected by current staging methods. The purpose of this study was to develop a system for detecting lymphogenic tumor cell dissemination in colorectal cancer. With the established CK 20-RT-PCR we detected tumor cells in 32 of 107 histopathologically negative lymph nodes from patients with colorectal cancer. We conclude that the CK 20-RT-PCR is more sensitive than immunohistochemical methods in detecting isolated disseminated tumor cells of colorectal cancer in lymph nodes. To evaluate the prognostic significance of lymphogenic disseminated tumor cells the examination and follow-up of more patients is necessary.