Furcation involvement is a condition in which periodontal fibre attachment is lost between the roots of multirooted teeth. It is defined as "bone resorption and attachment loss in interradicular space that results from plaque associated periodontal disease". Such a condition is reported to considerably increase the risk of tooth loss. Furcation involvement therefore presents both diagnostic and therapeutic dilemmas and represents a formidable problem in management of periodontal disease, principally related to complex and irregular anatomy of furcation. The etiology, diagnosis, treatment and prognosis of furcation involvement along with various complications faced in management of furcation involved molars are discussed in this book.