Prognosis is a prediction of the probable course, duration and outcome of a disease based on a general knowledge of the pathogenesis of the disease and the presence of risk factors for the disease. It is established after the diagnosis is made and before the treatment plan is established. Prognosis is often confused with the term risk. This chapter covers the determination, overall versus individual tooth prognosis, relationship between diagnosis and prognosis, and re-evaluation of prognosis after phase I therapy. Prognosis may be excellent, good, fair, poor, questionable, and hopeless. Prognosis can be divided into, overall prognosis and individual tooth prognosis. Factors that are to be considered, while determining the prognosis are overall clinical factors like age of the patient, disease severity, systemic restorative and environmental factors and local factors, patient compliance and prosthetic possibilities and factors influencing individual tooth prognosis are plaque or calculus, subgingival restorations, caries, nonvital teeth and root resorption.