Adhesion of disseminating tumor cells to the blood vascular endothelium is a pivotal step in metastasis. Previous investigations have shown that galectin-3 concentrations are increased in the bloodstream of patients with cancer and that galectin-3 promotes adhesion of disseminating tumor cells to vascular endothelium in vitro and experimental metastasis in vivo. This study determined the levels of galectin-1, -2, -3, -4, -8, and -9 in the sera of healthy people and patients with colon and breast cancer and assessed the influence of these galectins on cancer-endothelium adhesion.