We made a clinical study on 10 cases of histiocytosis syndrome who had been admitted to the pediatric department of Soon Chun Hyang University Hospital from Jan. 1982 to Dec. 1991. The results were obtained as follows 1) The sex incidence revealed male predominance with the ratio 4:1. 2) Among 10 cases, 4 cases were classified as eosinophilic granuloma, 1 case as Letterer-Siwe disease, 1 case as linfection associated hemophagocytic syndrome and 4 cases as malignant histiocytosis. 3) The mean age of symptom onset was 4 and 7/12 years in all disease group. 4) The common clinical symptoms and signs at dignosis were dyspnea, mass, pain on lower extremities and fever. 5) The most common organ involved among 9 organ systems was liver-spleen and the number of organ systems involved were 1 in 3 2 ases(30%), 3 in 2 cases(20%), 8 in 2 cases (20%) and 6, 7 and 10 organs in each 1 case. 6) The abnormal hematologic findings (Hb; 10g/dl and/or WBC; 4,000/mm3 and/or PLT; 100,000/mm3) were found in 6 cases. 7) Low serum albumin was found in 2 cases. Results of blood culture were Pseudomonas aeruginosae and Salmonella typhi in each 1 case. 8) The common findings on tissue biopsy were histiocytic proliferation and infiltration. 9) 4 patients of MH who recieved chemotherapy, a combination of adriamycin, vincristine, cyclophosphamide and prednisone were given in a total of four courses every 2 weeks ad induction therapy. When complete response was attained, a combination of adriamycin, vincristine, prednisone (AOP) and cyclophosphamide, vincristine, prednisone(COP) was administered alternately every 4 weeks as maintenance therapy for 6-64 months. 10) Among 4 patiens of MH who recieved chemotherapy, 1 patient was lost during induction chemotherapy, for 1 day.2 patients expired during induction chemotherapy, for 1 month, 1 patient expired during maintenance chemotherapty, for 8months, Eosinophilic granuloma cases (3) were recieved currettage and no recurrence. IAHS case due to typhoid fever was improved spontaneously.