Macrophages play essential roles in a wide variety of physiological and pathological processes. One of the unique features of these phagocytic leukocytes is their ability to fuse, forming multinucleated giant cells. Multinucleated giant cells are important mediators of tissue remodeling and repair and are also responsible for removal or sequestration of foreign material, intracellular bacteria and non phagocytosable pathogens, such as parasites and fungi. Depending upon the tissue where fusion occurs and the inflammatory result, multinucleated giant cells assume distinctly different phenotypes. Nevertheless, the ultimate outcome is the formation of large cells that can resorb bone tissue (osteolasts) or foreign material and pathogens (giant cells) extracellularly. The present review aims to concisely explain molecular mechanism of formation of giant cells and describes characteristic features of these cells in various diseases. Keywords: Langhan’s giant cells; Reed Sternberg cells; Touton giant cell; Xanthoma