Langerhans' cell histiocytosis is a relatively rare disorder of children, characterized by abnormal proliferation of Langerhans' cells. It usually presents as multiple osteolytic lesion with lymphadenopathy or cutaneous manifestations. We experienced a case of Langerhans' cell histiocytosis involving bone and lymph node, diagnosed by fine needle aspiration cytology of the lymph node. The patient was a 10-year old girl with left inguinal lymphadenopathy. Fine needle aspiration cytology from the lymph node disclosed very cellular smear consisted of Langerhans' cells, eosinophils and lymphocytes. The Langerhans' cells had eccentric oval to reniform shape nuclei with grooving and abundant pale cytoplasm. The diagnosis was confirmed later by histologic study of bone lesion.