Two cases of fibrous dysplasia of bone have been reported. The first represents a fibular lesion discovered incidentally, which illustrates varied histological patterns uncomplicated by fracture and repair. The manner of enlargement of the lesion, the participation of the periosteum, and other histological data have been presented. The second case, that in a girl showing precocious puberty and pigmented skin lesions, is a fibular lesion which progressed to pseudarthrosis and an adjoining but separate superficial tibial lesion. In this case, the differences in the histology of the two lesions and the effects of repair in obliterating the original histological appearance are discussed.