Histiocytosis X patients present with a variety of clinical manifestations and outcomes. The principal difficulty in the establishment of a definite protocol for treatment is based on the poor understanding of the basic nature of this disease, the absence of reliable prognostic criteria, and the problems with nomenclature. The objectives of this study were to analysis the course of the disease and the results of treatment in patients who had Langerhans cell histiocytosis and to suggest prognostic factors and guidelines for management. We reviewed the thirty patient who had Langerhans cell histiocytosis for past ten years. These patients were followed for an average 4.8 years (range, excluding patients who died of the disease, two to eleven years). The patients were divided into tow group; eighteen patients who Langerhans cell histiocytosis localized in skeleton (group I) and twelve patients who had Langerhans cell histiocytosis disseminate in both skeleton and extra-skeleton (group II). Methods of treatment included curettage with or without bone graft, radiotherapy, or watchful observation alone in group I; chemotherapy, chemotherapy and radiotherapy, or curettage in group II. All eighteen patients in group I had a complete response to the therapy. Seventeen of these eighteen patients had not a recurrence by the time of the latest follow-up examination; one had a recurrence. Four of twelve patients in group II had a complete response to the therapy, four had a partial response, and four had no response. Eight of these twelve patients had a recurrence; four did not. Two patients in group II died of the disease. The significant prognostic factor was the extent of the disease, limited to the skeleton or not, and the age of onset was an indirect prognostic factor predictin multiple organ involvement.