Mast cells are mobile, bone marrow derived, granule containing immune cells that are found in all connective tissue and mucosal environments and in peripheral and central nervous systems. Actions of mast cell chemical mediators include neoangiogenesis, recruitment of inflammatory cells and stimulation of fibroblasts. Mast cells count has been reported to be altered with variable results in studies conducted by researchers in various oral pathological conditions. The book attempts to provide an insight into various concepts or hypothesis proposed in such research related to mast cells in common oral pathological conditions especially oral pyogenic granuloma.