Osseous defects of the jaws following trauma, congenital deformity or pathology may show poor osteogenesis and the affected area may never be completely replaced by bone or will show alveolar height loss. The purpose of the present study was to evaluate the effect of allogenic bone implants (ABI) on the osteogenesis of jaw defects. Fifty-two patients (27 males, 25 females) with cystic lesions of the jaws were randomly divided into two groups: Group A underwent enucleation and packing with adsorbable gelatine sponge. Group B underwent enucleation and grafting with ABI. Both groups were evaluated radiographically. The height of the alveolar process was measured directly on the radiography. The density was measured with a digital densitometer. In Group A, the mandibular height at 6, 12 and 24 months postoperatively was 88%, 80% and 78% of the preoperative heights, respectively. In Group B, the heights were 95%, 93% and 90%, respectively. These differences were significant (P < 0.05-0.01). The density in Group B was significantly greater (P < 0.05-0.01) than in Group A at 6 and 12 months postoperatively. The difference at 24 months was not significant. On the basis of these findings, it can be concluded that ABI grafting of jaw defects enhances osteogenesis and prevents alveolar height loss in the mandible. ABI represent an encouraging alternative to autogenous bone grafting.