Forty-one patients with Langerhans Cell Histiocytosis (LCH) were treated over a thirty-one year period in our institution. These children were classified according to the number of systems involved: twenty-two had unisystem disease while nineteen had multisystem disease. A histological diagnosis was reached in 82% of cases, the remainder being diagnosed on both radiological and clinical grounds. 68% of those with multisystem disease had a rash at diagnosis whilst 64% had a persistent ear discharge. The diagnosis was established accidentally in 25% of those with unisystem disease. The mortality rate was 21% and was confined to those who were under two years of age at diagnosis, all of whom had multisystem disease. Morbidity was 20% and was restricted to patients with multisystem disease. Only one patient died within the last 10 years; there were no therapy related deaths. Treatment related morbidity was seen in only three children. In keeping with other series, our review has identified the following adverse prognostic factors a) age under 2 years at presentation, b) multisystem disease and c) major organ dysfunction. In view of the natural history of the disease, it is suggested that chemotherapy only be used in those patients who have major organ dysfunction or progressive disease and that radiotherapy is rarely indicated.