Some modification on the surgical technique for bone grafting to the alveolar clefts has been required. Secondary bone grafting was performed with and without free-periosteum on 34 (mean age, 9.8 +/- 1.1 years) and 44 (mean age, 10.7 +/- 1.2 years) alveolar clefts, respectively. Vertical bone formation which scored 3 or 4 was obtained in 97.1% of free-periosteum grafted clefts, while it was obtained in 79.5% of the control group. The rate of postoperative wound dehiscence in free-periosteum grafted clefts (20.6%) was not significantly different from the control group (11.4%). In the wound dehiscence cases, however, the grafted periosteum covered the grafted bone and prevented bone exposure. The score of bone formation in the free-periosteum grafted clefts (3.57 +/- 0.79) was significantly higher than that of the control group (2.60 +/- 1.34). Thus, free-periosteum grafting in secondary bone grafting is useful for bone formation in alveolar clefts.