Langerhans cell histiocytosis is a rare disease. Depending on which organs are involved, the disease may prove rapidly fatal, develop a chronic reactivating but therapy-responsive pattern or resolve spontaneously. Understanding of the pathology of the disease is progressing rapidly, and while clinical trials of standard chemotherapy agents continue, it is likely that novel targeted therapy will become feasible in the next decade. Permanent consequences of the disease are more commoner than generally realised.