The cure of a tumor patient with gastrointestinal cancer is dependent on the extension of the primary tumor (TNM-classification) and the option of curative resection (R0-resection) at the time of operation. The additional application of multimodal therapy approaches has lead to an improvement of prognosis in different advanced tumor stages. Nevertheless, despite curative tumor resection about 50% of patients with locally advanced gastrointestinal cancer develop recurrent tumor disease or distant metastases and die tumor-related. A possible explanation is the seed of disseminated tumor cells in blood, bone marrow or lymph nodes pre-, intra- or postoperatively, but also during diagnostic procedures. Several studies have shown in the last years that the presence of minimal residual disease (MRD) influences the course of disease and the patient's prognosis after curative tumor resection. Although several groups have reported the prognostic impact of disseminated tumor cells in the different compartments of bone marrow, lymph nodes and blood, the phenomenon of minimal residual disease is not acknowledged as an established prognostic factor and is not integrated into the classification of the UICC. Therefore, no therapeutic consequences were drawn at present from the detection of disseminated tumor cells in patients with gastrointestinal cancer. A possible explanation are missing multi-center-studies, which confirm the results of the several single-center-studies. Standardization of study designs and methodical procedures and the evidence of reproduction are mandatory in order to value and interpret the multitude of studies and the available data in this field. Only these results will allow to decide if the presence and detection of disseminated tumor cells can alter the tumor staging and individualize or possibly minimize further oncological therapy strategies.