Since the fibro-osseous lesion is not a specific diagnostic term, the author studied clinically and radiologically 44 cases which had been diagnosed as fibro-osseous lesion in SNUDH (1972- 1981. 12).The obtained results were as follows. 1. Clinico-radiologically, the cases of fibro-osseous lesions were divided into two groups. 2. The first group was fibrous dysplasia (21 cases). 3. The second group was tumors of periodontal ligament origin, including ossifying fibroma, cementifying fibroma and cemento-ossifying fibroma (23 cases). 4. In most cases the chief complaint was painless swelling of the jaw and the mean age of the fibrous dysplasia (24.6 yrs) was a little younger than that of the periodontal ligament origin lesions (29.2 yrs). 5. In fibrous dysplasia, maxilla was more often involved and showed ground-glass or smoke pattern radiologically. 6. The tumors of periodontal ligament origin occurred more in female, mandible and radiologically showed varying amounts of radiopaque foci in well-circumscribed osteolytic lesion.