Galectins are a family of animal lectins defined by shared characteristic amino-acid sequences and affinity for β-galactose-containing oligosac-charides. Galectin-3, a 31-kDa member of the β-galactoside-binding proteins, contains one carbohydrate recognition domain (CRD) and a proline- and glycine-rich N-terminal domain through which is able to form oligomers. Galectin-3 is widely expressed in many normal tissues and a variety of tumors. It is found intracellularly in nucleus and cytoplasm or secreted outside of cell, being present on the cell surface or in the extracellular space. Galectin-3 is involved in various biological processes including cell growth, adhesion, differentiation, apoptosis, angiogenesis, immune response, neoplastic transformation and metastasis. Elevated serum galectin-3 levels have been reported in patients with breast, gastrointestinal, lung, or ovarian cancer, melanoma, and non-Hodgkin’s lymphoma.