Introduction: This study examined the effect of recombinant human bone morphogenetic protein (rhBMP)-2 and $eta$-tricalcium phosphate ($eta$-TCP) on new bone formation in a rabbit calvarium using a rapid prototype titanium cap (RP Ti cap). Materials and Methods: Eight New Zealand white rabbits were used in this study. Hemispherical RP Ti caps (10 mm in diameter) were implanted subperiosteally on the rabbit calvaria. $eta$-TCP was filled in the RP Ti cap in the control group, and rhBMP-2 soaked $eta$-TCP was used in experimental group. The rabbits were sacrificed 2 and 4 weeks after the operation. The volume and pattern of newly formed bone was analyzed by micro computed tomography (CT). Results: Macroscopically, there were no abnormal findings in any of the animals. The micro CT images revealed new bone from the calvaria that expanded gradually toward the top of the titanium cap, particularly along the inner surface of the titanium cap in the experimental group at 4 weeks after grafting. There was no significant difference in new bone volume ratio between the control and experimental groups at 2 weeks after grafting. There was a statistically significant difference in the new bone volume ratio between the experimental ($14.1{pm}1.8;%$) and control ($7.2{pm}1.5;%$) groups at 4 weeks after grafting (P<0.01). Conclusion: The RP Ti cap can effectively guide new bone formation and rhBMP-2 can induce the new bone formation.