Purpose: The aim of this study was to compare a bovine bone substitute (Bio-Oss) to autogenous bone with respect to its value as a material for sinus augmentation. Materials and Methods: In 10 beagle dogs 12 months of age, the 3 maxillary premolars were extracted on both sides. Six weeks later, 2 cavities of predefined size were produced in the region of the nasal cavity. The antral window was 25 mm long and had a vertical extension of 7 mm. Two Frialit-2 implants (3×8 mm) were placed in each bone defect (n = 20). Every implant was primarily stable because of fixation in native bone. In each maxilla, 1 bone defect was filled with autogenous bone harvested from the mandible and 1 was filled with Bio- Oss (material selected at random). The animals were sacrificed at 90 and 180 days, and histologic specimens were examined and the results subjected to statistical analysis by the WiIcoxon test for paired observations. Results: No healing problems were observed. Histologically, after 90 days the volume of the augmentation showed a reduction of 14.6 ± 4.4% within the Bio-Oss group and 3.8 ± 2.5% in the group with autogenous bone. Bone-implant contact of 52.16 ± 13.15% in the Bio-Oss group and 60.21 ± 11.46% in the autogenous bone group was observed. At 180 days, the Bio-Oss group showed bony ingrowth of the substitute, whereas in the autogenous group a differentiation from original bone could no longer be made. The volume reduction was 16.5 ± 8.67% in the Bio-Oss group and 39.8 ± 16.14% in the autogenous group. Bone-implant contact of 63.43 ± 19.56% in the Bio-Oss group and 42.22 ± 12.80% in the autogenous bone group was measured. Discussion and Conclusion: The results indicated that because of the nonresorptive properties of the bone substitute Bio-Oss, regeneration of the defects is achievable. It was demonstrated that the bone substitute seemed to behave as a permanent implant. The volume of the area augmented by autogenous bone decreased over the observation period.