1. Twenty-eight cases of eosinophilic granuloma of bone in children and adults, all but one with symptomatically solitary lesions, are reported. The skull, femur, ribs, and mandible were the most frequent sites of involvement.
2. No diagnostic roentgenographic characteristics were found. Lesions of the flat bones were generally punched-out osteolytic lesions. Lesions of long bones were easily confused with malignant tumors. Biopsy is considered imperative to establish the diagnosis.
3. Transition of eosinophilic granuloma to Hand-Schüller-Christian disease or Abt-Letterer-Siwe syndrome has not been encountered in these cases and we have some doubts whether the reported cases of transition represent true changes from one form to another.
4. Therapy has included excision, curettage, small doses of irradiation, or nothing. Evaluation of any one form of treatment is impossible. All the lesions reported in this study healed regardless of the therapy.
5. Meticulous microbiological studies of the tissue from these lesions seem indicated.