Galectin-1 is one of the most important lectins to date participating in the malignant tumor development. With more and more data available on its expression in tumors it is already clear that this lectin is an important target for cancer diagnostics and treatment.Its first involvement in cancer was associated with cell adhesion. Later on the lectin was shown to induce apoptosis of activated T-cells, and experiments have confirmed that cancer cells express galectin-1 also to protect themselves from immune response. Latest finding is a participation of galectin-1 in tumor angiogenesis as an angiogenic factor. In most of the cases described, galectin-1 is up-regulated in tumors in comparison to normal tissue. Moreover, the presence of the lectin is associated with metastases and poor prognosis of disease outcome.