To evaluate the pinhole scintigraphic findings and its significance, authors retros- pectively compared the pinhole bone scintigrams and corresponding radiograms of 16 lesions in 14 patients with fibrous dysplasia. They were diagnosed pathologically in 10 lesions and radiologically in 6 lesions. The mean age of patients was 41.1 years. The mean interval between two studies was 1.1 days. Locations were ribs 7, pelvic bone 4, clavicle l, long bones 4(femur 2, titbia 1, humerus 1). The radiographic findings were as follows :the central portions were radiolucent(n=9), ground-glass opacities(n=5) or sclerotic(n=2) and the peripheral appearance were sclerotic rim(n-5), septation(n=7), cortical perforation (n=10) and invisible cortical thinning(n=9). Pinhc>le scintigraphic findings were as follows : Central portions showed normal 1+ uptake in 6 cases(radiolucent 5, ground-glass opacity 1), slightly increased 2+ uptake in cases(radiolucent 4, ground-glass opacity 3), and marked 3+ uptake in,3 cases(ground-glass opacity 1, sclerotic 2). The 15 of 16 lesions showed more intense uptake in the peripheral portion : slightly increased 2+ uptake corresponding to the sclerotic rim(5/5) and unvisible cortical thinning(1/9), and irregular foci of marked 3 + uptake corresponding to septation(7/7), cortical perforation(10/10) and invisible cortical thinning (8/9). One of 16 lesions showed homogeneous 2t uptake. In conclusion, pinhole scintigram provides information on regional activity of the fibrous dysplasia, which would be helpful in diagnosis, prediction of prognosis and determination of treatment plan.