Various synthetic materials were developed to be used for implant dentistry and periodontal treatments. Among the various synthetic bone substitutes, calcium phosphate ceramics have been extensively investigated because their mineral chemistry resembles that of human bone. We evaluated the regeneration of three calcium phosphate synthetic block bone grafts in rabbit calvarial noncritical size defects. Four 8-mm-diameter defects were created in each rabbit (N = 10). Three defects, hydroxyapatite (HA), beta-tricalcium phosphate (β-TCP), and biphasic calcium phosphate (BCP), were randomly filled with one of three fabricated synthetic block bone graft materials. The fourth defect was filled with blood clots. Specimens were harvested at 4 and 8 weeks postsurgery. Histological and histometrical findings indicated that all three calcium phosphate block bone graft materials were able to maintain space significantly better than the control group at both 4 and 8 weeks. In the BCP group, the amount of newly formed bone was increased more than for the other groups. Additionally, β-TCP showed a large resorption of graft materials after 4 weeks postsurgery, while there were only small resorption for HA and BCP. © 2012 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2012.