Purpose: This study investigated the combination of a bone marrow mononuclear fraction with a bone xenograft material in an appositional bone regeneration technique. Materials and Methods: Twelve New Zealand rabbits were randomly divided into two groups of six animals each. Bone reconstruction situations were created using titanium cylinders; these were filled with xenograft in group 1 animals and xenograft enriched with bone marrow mononuclear fraction in group 2 animals. Two cylinders were adapted onto the calvaria of each animal. Bone marrow aspirate was obtained from the tibia of every animal. After 8 weeks, the animals were sacrificed and the parietal bone and cylinders were fixed in 10% formalin for analysis of clinical measurement of the bone volume formed inside the cylinders and histomorphometric evaluation of parameters such as vital mineralized tissue (VMT), nonvital mineralized tissue (NVMT), nonmineralized tissue (NMT), and vital mineralized tissue in contact with titanium (VMTCT). Results: Clinically, groups 1 and 2 demonstrated bone volume gains of 88.29% ± 25.97% and 98.96% ± 0.00%, respectively. Histomorphometry for groups 1 and 2, respectively, demonstrated the following mean values: VMT, 18.96% ± 8.99% and 28.02% ± 8.76%; NVMT, 28.43% ± 2.44% and 25.57% ± 2.33%; NMT, 52.61% ± 10.80% and 46.42% ± 10.06%; and VMTCT, 4.98% ± 4.30% and 27.29% ± 9.58%. Conclusion: The results of this study suggest that the use of the bone marrow mononuclear fraction can improve bone healing and the level of osseointegration. Keywords: bone marrow, bone regeneration, cell transplantation, stromal cells