Fifty histologically proved cases of eosinophilic granuloma of bone were studied. Male patients outnumbered females, 31 to 19. Ages ranged from 8 months to 53 years (average, 14 years). Only 9 patients thought that the onset was caused by trauma. Pathologic fractures occurred in 7. Eosinophilia was noted in only 5 cases. Treatment was by surgery, radiotherapy, and chemotherapy. Symptoms usually subsided within 2 weeks after treatment, and the average healing period for solitary lesions was 16 months.