The current status of lymphatic mapping and sentinel node biopsy in the treatment of patients with malignant melanoma and breast cancer is described. The possible use of a similar method in patients with colorectal and gastric cancer is outlined. Peroperative lymphatic mapping and identification of sentinel node(s) in patients with gastrointestinal cancer may lead to modified (tailored) resections and extended lymph node dissections only in those patients in whom the sentinel node(s) contains tumour cells. The method offers the possibility of improving staging by identification of patients with early disseminated disease who should be considered for adjuvant treatment or be included in trials of adjuvant treatment to speed up the breakthrough of more effective adjuvant regimens. Large studies are needed to find out if the sentinel node concept is as valid in gastrointestinal cancer as studies so far have shown that it is for malignant melanoma and breast cancer.