Galectin-3 is a β-galactoside-binding animal lectin that contains carbohydrate-recognition domains and displays multiple related functions. It has important roles in diverse biological events, such as embryogenesis, growth, cell adhesion, proliferation, differantiation, cell-cycle progression, apoptosis, mRNA splicing, and regulation of the immune system. Galectin-3 is expressed in various cells and tissues, such as activated macrophages, eosinophils, neutrophils, mast cells, epithelium of the gastrointestinal and respiratory tracts, kidneys and some sensory neurons, and is also involved in tumorigenesis, angiogenesis, and tumor metastasis. In this review of the literature, immunohistochemical Galectin-3 expression is investigated in numerous tumors and disorders of various organ systems.