Fifteen pediatric cases of vertebral involvement in histiocytosis X are reported. The study of these cases and a review of the literature shows that every patient with histiocytosis X should have a local and systemic staging work-up to differentiate isolated eosinophilic granulomas of the bone, multiple eosinophilic granulomas of the bone, and visceral disseminated disease. Management varies according to the extension of the disease. Systemic chemotherapy may be indicated in patients with extraosseous lesions. Local investigations should be performed to look for instability of the spine, which may require surgery, and above all for spread to the soft parts indicating chemotherapy with or without surgery. Forms which are strictly confined to the bone and cause no instability, such as vertebra plana, require no treatment.