Several types of bone grafts are used in ridge preservation procedures.To compare the healing of allografts and xenografts applied for alveolar ridge preservation.Twenty volunteers in need of extraction of a single-rooted tooth prior to implant installation were randomized into two groups. One group received a deproteinized cancellous bovine bone xenograft embedded in a 10% collagen matrix and the other a demineralized freeze-dried cortical bone allograft. A collagen membrane was used to cover the grafts, flaps were sutured. At baseline and 6 months later, clinical measurements including vertical and horizontal bone dimensions were taken. Histomorphometric analysis was performed.Both groups showed shrinkage of bone dimensions. At mesial, center and distal sites, the vertical changes in dimension were -0.6, 0.5, and -0.1 mm for the allograft and -1.1, -0.4, and -0.9 mm for the xenograft. The horizontal changes in dimensions were -1.4 mm for the allograft and -2.6 mm for the xenograft. New bone and residual graft material were 25.5 ± 10.1% and 33.8 ± 9.4% at the allograft and 35.3 ± 16.8% and 22.2 ± 13.4% at the xenograft sites. None of the differences was statistically significant.Both grafting materials are suitable for the preservation of the alveolar ridge.