Galectin-3 is a member of a family of beta-galactoside-binding animal lectins and is distinct from other members by the presence of tandem repeats in its N-terminal region. Like other members, galectin-3 lacks a classical signal sequence, but the protein is secreted by a nonclassical secretary pathway and can function extracellularly in an autocrine or paracrine fashion. Galectin-3 is able to oligomerize and participate in multivalent interactions with cell surface and extracellular matrix glycans, through lectin-carbohydrate interactions, thus affecting cellular functions. Galectin-3 is detectable in the cytosol and nucleus and the intracellular protein may bind to other cytoplasmic and nuclear proteins by protein-protein interactions. In this manner, galectin-3 is able to influence intracellular signaling pathways and exert various functions. Galectin-3 is expressed by virtually all immune and inflammatory cell types, either constitutively or in a inducible fashion. A large body of work has demonstrated the role of galectin-3 in regulation of the functions of these cells. The use of galectin-3-deficient mice has provided additional evidence for this protein's contribution to the inflammatory response. Thus, galectin-3 may be a therapeutic target for various inflammatory diseases.