It is extremely necessary to find an ideal filling material for the treatment of benign bone defect, particularly those benign osteolytic defect in children with a comparatively large cavity. From July, 1995 to December, 1996, 10 cases of benign osteolytic bone defects were treated, in which 5 cases of benign osteolytic defects, 3 cases of bone cysts, 1 case of fibrous dysplasia of bone and 1 case of non-ossifying fibroma. After through curettage of the cavity, the natural non-organic bone in cube-shaped was used to fill the prepared cavity. The results showed that the activities of the patients resumed normal in 3 to 6 months after operation. The roentgenographic examination after operation showed that the lucent spaces between NNB cubes disappeared with obvious new bone formation and the bony cavity was obliterated with newly-formed bone. There was no recurrence of the lesion during a follow-up of 7 to 24 months. It was concluded that to treat the osteolytic defect of bone with NNB was a method of choice. The new bone formation appeared early in large amount and increased rapidly.