Langerhans cell histiocytosis is a rare proliferative disorder where pathologic Langerhans cells accumulate in a variety of organs. Historically, the nomenclature regarding this entity has been confusing because the disease had been subcategorized simply based upon the different clinical manifestations. In the following article, we summarize the current recommendation of the Histiocyte Society regarding the classification, evaluation, prognosis, and treatment of Langerhans cell histiocytosis.