Report on a case of a patient, white, eleven years old, girl and brasilian, who came to the Service complaining of pain in both legs, at the level of the knee joint in a period of two years time. After an accurate orthopaedic examen the focal place was detected at the level of the proximal end of the fibula. The radiogram confirmed the existence of an osteolitic lesion in the superior end of the fibula, right side, in a cortical position and surrounded by a sclerotic area. The surgical removal was performed and the pathological examens confirmed to be a benign osteoblastoma. The postoperative evolution was normal and uneventfull. The radiograms demonstrate that in a three years period the healing of the bone was normal and total. No graft used and the periostal activity was the main source of bone formation.